MPLS LSP Ping/Traceroute for LDP/TE, and LSP
Ping for VCCV
First Published: January 26, 2004
Last Updated: August 30, 2007
The MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV feature helps service providers
monitor label switched paths (LSPs) and quickly isolate Multiprotocol Label Switching (MPLS)
forwarding problems.
The feature provides the following capabilities:
Note
•
MPLS LSP Ping to test LSP connectivity for IPv4 Label Distribution Protocol (LDP) prefixes,
Resource Reservation Protocol (RSVP) traffic engineering (TE), and Any Transport over MPLS
(AToM) forwarding equivalence classes (FECs).
•
MPLS LSP Traceroute to trace the LSPs for IPv4 LDP prefixes and RSVP TE prefixes.
Software images for Gigabit Switch Routers (GSRs) have been deferred to Cisco IOS
Release 12.0(27)S1.
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. To reach
links to specific feature documentation in this module and to see a list of the releases in which each feature is
supported, use the “Feature Information for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for
VCCV” section on page 87.
Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV, page 2
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© 2004-2007 Cisco Systems, Inc. All rights reserved.
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Prerequisites for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
•
Restrictions for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV, page 2
•
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV, page 3
•
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV, page 10
•
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV,
page 33
•
Additional References, page 60
•
Command Reference, page 62
•
Glossary, page 88
•
Feature Information for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV, page 87
Prerequisites for MPLS LSP Ping/Traceroute for LDP/TE, and
LSP Ping for VCCV
Before you use the MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV feature, you
should:
•
Determine the baseline behavior of your MPLS network. For example:
– Expected MPLS experimental (EXP) treatment.
– Expected maximum size packet or maximum transmission unit (MTU) of the label switched
path.
– The topology, expected label switched path, and number of links in the LSP. Trace the paths of
the label switched packets including the paths for load balancing.
•
Understand how to use MPLS and MPLS applications. You need to:
– Know how LDP is configured.
– Understand AToM concepts.
•
Understand label switching, forwarding, and load balancing.
Before using the ping mpls or trace mpls command, you must ensure that the router is configured to
encode and decode MPLS echo packets in a format that all receiving routers in the network can
understand.
Restrictions for MPLS LSP Ping/Traceroute for LDP/TE, and LSP
Ping for VCCV
•
You cannot use MPLS LSP traceroute to trace the path taken by AToM packets. MPLS LSP
traceroute is not supported for AToM. (MPLS LSP ping is supported for AToM.) However, you can
use MPLS LSP traceroute to troubleshoot the Interior Gateway Protocol (IGP) LSP that is used by
AToM.
•
You cannot use MPLS LSP ping to validate or trace MPLS Virtual Private Networks (VPNs).
•
You cannot use MPLS LSP traceroute to troubleshoot LSPs that employ time-to-live (TTL) hiding.
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
•
MPLS supports per-destination and per-packet (round robin) load balancing. If per-packet load
balancing is in effect, you should not use MPLS LSP traceroute because LSP traceroute at a transit
router consistency checks the information supplied in the previous echo response from the directly
connected upstream router. When round robin is employed, the path that an echo request packet
takes cannot be controlled in a way that allows a packet to be directed to TTL expire at a given router.
Without that ability, the consistency checking may fail during an LSP traceroute. A consistency
check failure return code may be returned.
•
A platform must support LSP ping and traceroute in order to respond to an MPLS echo request
packet.
•
Unless the MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV feature is enabled
along the entire path, you cannot get a reply if the request fails along the path at any node.
•
There are certain limitations when a mixture of draft versions are implemented within a network.
The version of the draft must be compatible with Cisco’s implementation. Due to the way the LSP
Ping draft was written, earlier versions may not be compatible with later versions because of
changes to type, length, values (TLVs) formats without sufficient versioning information. Cisco
attempts to compensate for this in its implementations by allowing the sending and responding
routers to be configured to encode and decode echo packets assuming a certain version.
•
The network should not use TTL hiding if you want to use MPLS LSP traceroute.
Information About MPLS LSP Ping/Traceroute for LDP/TE, and
LSP Ping for VCCV
Before using the MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV feature, you need
an understanding of the following concepts:
•
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV Functionality, page 3
•
MPLS LSP Ping Operation, page 4
•
MPLS LSP Traceroute Operation, page 5
•
MPLS Network Management with MPLS LSP Ping and MPLS LSP Traceroute, page 7
•
Any Transport over MPLS Virtual Circuit Connection, page 7
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV Functionality
Internet Control Message Protocol (ICMP) ping and traceroute are often used to help diagnose the root
cause when a forwarding failure occurs. However, they are not well suited for identifying LSP failures
because an ICMP packet can be forwarded via IP to the destination when an LSP breakage occurs.
The MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV feature is well suited for
identifying LSP breakages for the following reasons:
•
An MPLS echo request packet cannot be forwarded via IP because IP TTL is set to 1 and the IP
destination address field is set to a 127/8 address.
•
The FEC being checked is not stored in the IP destination address field (as is the case of ICMP).
MPLS echo request and reply packets test LSPs. There are two methods by which a downstream router
can receive packets:
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
•
The Cisco implementation of MPLS echo request and echo reply that was previously based on the
Internet Engineering Task Force (IETF) Internet Draft Detecting MPLS Data Plane Failures
(draft-ietf-mpls-lsp-ping-03.txt). This is documented in the “MPLS Embedded Management—LSP
Ping/Traceroute and AToM VCCV” feature module.
•
Features described in this document that are based on the IETF RFC 4379 Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures:
– Echo request output interface control
– Echo request traffic pacing
– Echo request end-of-stack explicit-null label shimming
– Echo request request-dsmap capability
– Request-fec checking
– Depth limit reporting
MPLS LSP Ping Operation
MPLS LSP ping uses MPLS echo request and reply packets to validate an LSP. You can use MPLS LSP
ping to validate IPv4 LDP, AToM, and IPv4 RSVP FECs by using appropriate keywords and arguments
with the ping mpls command.
The MPLS echo request packet is sent to a target router through the use of the appropriate label stack
associated with the LSP to be validated. Use of the label stack causes the packet to be forwarded over
the LSP itself.
The destination IP address of the MPLS echo request packet is different from the address used to select
the label stack. The destination IP address is defined as a 127.x.y.z/8 address. The 127.x.y.z/8 address
prevents the IP packet from being IP switched to its destination if the LSP is broken.
An MPLS echo reply is sent in response to an MPLS echo request. The reply is sent as an IP packet and
it is forwarded using IP, MPLS, or a combination of both types of switching. The source address of the
MPLS echo reply packet is an address obtained from the router generating the echo reply. The
destination address is the source address of the router that originated the MPLS echo request packet.
The MPLS echo reply destination port is set to the echo request source port.
Figure 1 shows MPLS LSP ping echo request and echo reply paths.
Figure 1
MPLS LSP Ping Echo Request and Echo Reply Paths
LSP
LSR2
LSR3
LSR4
MPLS echo request
LSR9
LSR8
LSR7
MPLS echo reply via IP, MPLS, or a combination of IP + MPLS
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
4
LSP tailend
LSR6
MPLS echo reply
Target router
Originating
router
LSR10
LSR5
103387
LSP headend
LSR1
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
If you initiate an MPLS LSP ping request at LSR1 to a FEC at LSR6, you get the results shown in
Table 1.
Table 1
MPLS LSP Ping Example from Figure 1
Step
Router
Action
1.
LSR1
Initiates an MPLS LSP ping request for an FEC at the target router LSR6 and
sends an MPLS echo request to LSR2.
2.
LSR2
Receives the MPLS echo request packet and forwards it through transit routers
LSR3 and LSR4 to the penultimate router LSR5.
3.
LSR5
Receives the MPLS echo request, pops the MPLS label, and forwards the packet
to LSR6 as an IP packet.
4.
LSR6
Receives the IP packet, processes the MPLS echo request, and sends an MPLS
echo reply to LSR1 through an alternate route.
5.
LSR7 to
LSR10
Receives the MPLS echo reply and forwards it back toward LSR1, the originating
router.
6.
LSR1
Receives the MPLS echo reply in response to its MPLS echo request.
MPLS LSP Traceroute Operation
MPLS LSP traceroute uses MPLS echo request and reply packets to validate an LSP. You can use MPLS
LSP traceroute to validate IPv4 LDP and IPv4 RSVP FECs by using appropriate keywords and
arguments with the trace mpls command.
The MPLS LSP Traceroute feature uses TTL settings to force expiration of the TTL along an LSP. MPLS
LSP Traceroute incrementally increases the TTL value in its MPLS echo requests (TTL = 1, 2, 3, 4) to
discover the downstream mapping of each successive hop. The success of the LSP traceroute depends
on the transit router processing the MPLS echo request when it receives a labeled packet with a TTL =
1. On Cisco routers, when the TTL expires, the packet is sent to the Route Processor (RP) for processing.
The transit router returns an MPLS echo reply containing information about the transit hop in response
to the TTL-expired MPLS packet.
The MPLS echo reply destination port is set to the echo request source port.
Note
When a router traces an IPV4 FEC that goes over a traffic engineering tunnel, intermediate routers may
return U (unreachable) if LDP is not running in those intermediate routers.
Figure 2 shows an MPLS LSP traceroute example with an LSP from LSR1 to LSR4.
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Figure 2
MPLS LSP Traceroute Example
LSP
1
LSR1
2
LSR2
LSR1
5
LSR2
LSR3
LSP
7
6
TTL=3
LSR1
9
LSR4
LSP
4
3
TTL=2
LSR3
LSR2
LSR4
8
LSR3
LSR4
103388
TTL=1
If you enter an LSP traceroute to an FEC at LSR4 from LSR1, you get the results shown in Table 2.
Table 2
MPLS LSP Traceroute Example Based on Figure 2
Step
Router
MPLS Packet Type and Description
1.
LSR1
MPLS echo request—With a target
FEC pointing to LSR4 and to a
downstream mapping
•
Sets the TTL of the label stack to 1
•
Sends the request to LSR2
MPLS echo reply
•
Receives the packet with a TTL = 1
•
Processes the User Datagram Protocol (UDP) packet as an
MPLS echo request
•
Finds a downstream mapping and replies to LSR1 with its own
downstream mapping, based on the incoming label
MPLS echo request—With the same
target FEC and the downstream
mapping received in the echo reply
from LSR2
•
Sets the TTL of the label stack to 2
•
Sends the request to LSR2
MPLS echo request
•
Receives the packet with a TTL = 2
•
Decrements the TTL
•
Forwards the echo request to LSR3
•
Receives the packet with a TTL = 1
•
Processes the UDP packet as an MPLS echo request
•
Finds a downstream mapping and replies to LSR1 with its own
downstream mapping based on the incoming label
•
Sets the TTL of the packet to 3
•
Sends the request to LSR2
2.
LSR2
3.
LSR1
4.
LSR2
5.
LSR3
6.
LSR1
MPLS reply packet
MPLS echo request—With the same
target FEC and the downstream
mapping received in the echo reply
from LSR3
Router Action (Receive or Send)
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Table 2
MPLS LSP Traceroute Example Based on Figure 2 (continued)
Step
Router
MPLS Packet Type and Description
7.
LSR2
MPLS echo request
8.
9.
LSR3
LSR4
MPLS echo request
MPLS echo reply
Router Action (Receive or Send)
•
Receives the packet with a TTL = 3
•
Decrements the TTL
•
Forwards the echo request to LSR3
•
Receives the packet with a TTL = 2
•
Decrements the TTL
•
Forwards the echo request to LSR4
•
Receives the packet with a TTL = 1
•
Processes the UDP packet as an MPLS echo request
•
Finds a downstream mapping and also finds that the router is
the egress router for the target FEC
•
Replies to LSR1
MPLS Network Management with MPLS LSP Ping and MPLS LSP Traceroute
To manage an MPLS network, you must have the ability to monitor LSPs and quickly isolate MPLS
forwarding problems. You need ways to characterize the liveliness of an LSP and reliably detect when
an LSP fails to deliver user traffic.
You can use MPLS LSP ping to verify the LSP that is used to transport packets destined for IPv4 LDP
prefixes, and AToM PW FECs. You can use MPLS LSP traceroute to trace LSPs that are used to carry
packets destined for IPv4 LDP prefixes.
An MPLS echo request is sent through an LSP to validate it. A TTL expiration or LSP breakage causes
the transit router to process the echo request before it gets to the intended destination. The router returns
an MPLS echo reply that contains an explanatory reply code to the originator of the echo request.
The successful echo request is processed at the egress of the LSP. The echo reply is sent via an IP path,
an MPLS path, or a combination of both back to the originator of the echo request.
Any Transport over MPLS Virtual Circuit Connection
AToM VCCV allows you to send control packets inband of an AToM PW from the originating provider
edge (PE) router. The transmission is intercepted at the destination PE router, instead of being forwarded
to the customer edge (CE) router. This capability allows you to use MPLS LSP ping to test the PW
section of AToM virtual circuits (VCs).
LSP ping allows verification of AToM VC setup by FEC 128 or FEC 129. FEC 128-based AToM VCs
can be set up by using LDP for signaling or by using a static pseudowire configuration without using any
signaling component on the two endpoints. Cisco IOS does not distinguish between FEC 128 and
FEC 129 static pseudowires while issuing MPLS ping; the same commands are used.
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
AToM VCCV consists of the following:
•
A signaled component in which the AToM VCCV capabilities are advertised during VC label
signaling
•
A switching component that causes the AToM VC payload to be treated as a control packet
AToM VCCV Signaling
One of the steps involved in AToM VC setup is the signaling or communication of VC labels and AToM
VCCV capabilities between AToM VC endpoints. To communicate the AToM VCCV disposition
capabilities of each endpoint, the router uses an optional parameter, defined in the Internet Draft
draft-ieft-pwe3-vccv-01.txt.
The AToM VCCV disposition capabilities are categorized as follows:
•
Applications—MPLS LSP ping and ICMP ping are applications that AToM VCCV supports to send
packets inband of an AToM PW for control purposes.
•
Switching modes—Type 1 and Type 2 are switching modes that AToM VCCV uses for
differentiating between control and data traffic.
Table 3 describes AToM VCCV Type 1 and Type 2 switching modes.
Table 3
Type 1 and Type 2 AToM VCCV Switching Modes
Switching Mode Description
Type 1
Uses a Protocol ID (PID) field in the AToM control word to identify an AToM
VCCV packet
Type 2
Uses an MPLS Router Alert Label above the VC label to identify an AToM VCCV
packet
Selection of AToM VCCV Switching Types
Cisco routers always use Type 1 switching, if available, when they send MPLS LSP ping packets over
an AToM VC control channel. Type 2 switching accommodates those VC types and implementations that
do not support or interpret the AToM control word.
Table 4 shows the AToM VCCV switching mode advertised and the switching mode selected by the
AToM VC.
Table 4
AToM VCCV Switching Mode Advertised and Selected by AToM VC
Type Advertised
Type Selected
AToM VCCV not supported
—
Type 1 AToM VCCV switching
Type 1 AToM VCCV switching
Type 2 AToM VCCV switching
Type 2 AToM VCCV switching
Type 1 and Type 2 AToM VCCV
switching
Type 1 AToM VCCV switching
An AToM VC advertises its AToM VCCV disposition capabilities in both directions: that is, from the
originating router (PE1) to the destination router (PE2), and from PE2 to PE1.
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Information About MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
In some instances, AToM VCs might use different switching types if the two endpoints have different
AToM VCCV capabilities. If PE1 supports Type 1 and Type 2 AToM VCCV switching and PE2 supports
only Type 2 AToM VCCV switching, there are two consequences:
•
LSP ping packets sent from PE1 to PE2 are encapsulated with Type 2 switching.
•
LSP ping packets sent from PE2 to PE1 use Type 1 switching.
You can determine the AToM VCCV capabilities advertised to and received from the peer by entering
the show mpls l2transport binding command at the PE router.
Information Provided by the Router Processing LSP Ping or LSP Traceroute
Table 5 describes the characters that the router processing an LSP ping or LSP traceroute packet returns
to the sender about the failure or success of the request.
You can also display the return code for an MPLS LSP Ping operation if you enter the verbose keyword
in the ping mpls command.
Table 5
Note
Echo Reply Return Codes
Output Code
Echo Return
Code
Meaning
x
0
No return code.
M
1
Malformed echo request.
m
2
Unsupported TLVs.
!
3
Success.
F
4
No FEC mapping.
D
5
DS Map mismatch.
I
6
Unknown Upstream Interface index.
U
7
Reserved.
L
8
Labeled output interface.
B
9
Unlabeled output interface.
f
10
FEC mismatch.
N
11
No label entry.
P
12
No receive interface label protocol.
p
13
Premature termination of the LSP.
X
unknown
Undefined return code.
Echo return codes 6 and 7 are accepted only for Version 3 (draft-ieft-mpls-ping-03).
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and
LSP Ping for VCCV
This section contains the following tasks:
•
Enabling Compatibility Between the MPLS LSP and Ping or Traceroute Implementation, page 10
(required)
•
Validating an FEC by Using MPLS LSP Ping and MPLS LSP Traceroute, page 12 (required)
•
Using DSCP to Request a Specific Class of Service in an Echo Reply, page 14 (optional)
•
Controlling How a Responding Router Replies to an MPLS Echo Request, page 16 (optional)
•
Preventing Loops when Using MPLS LSP Ping and LSP Traceroute Command Options, page 18
(optional)
•
Detecting LSP Breaks, page 20 (optional)
Enabling Compatibility Between the MPLS LSP and Ping or Traceroute
Implementation
LSP ping drafts after Version 3 (draft-ietf-mpls-ping-03) have undergone numerous TLV format
changes, but the versions of the draft do not always interoperate.
To allow later Cisco implementations to interoperate with draft Version 3 Cisco and non-Cisco
implementations, a global configuration mode lets you encode and decode echo packets in formats
understood by draft Version 3 implementations.
Unless configured otherwise, a Cisco implementation encodes and decodes echo requests assuming the
version on which the IETF implementations is based.
To prevent failures reported by the replying router due to TLV version issues, you should configure all
routers in the core. Encode and decode MPLS echo packets in the same draft version. For example, if
the network is running RFC 4379 (Cisco Version 4) implementations but one router is capable of only
Version 3 (Cisco Revision 3), configure all routers in the network to operate in Revision 3 mode.
The Cisco implementation of MPLS echo request and echo reply is based on the IETF RFC 4379. IEFT
drafts subsequent to this RFC (drafts 3, 4, 5, 6, and 7) introduced TLV format differences. These
differences could not be identified because the echo packet had no way to differentiate between one TLV
format and another TLV format. This introduced limited compatibility between the MPLS LSP
Ping/Traceroute implementations in the Cisco IOS 12.0(27)S1 and 12.0(27)S2 releases and the MPLS
ping or traceroute implementation in later Cisco IOS releases. To allow interoperability between these
releases, a revision keyword was added for the ping mpls and trace mpls commands. The revision
keyword enables Cisco IOS releases to support the existing draft changes and any changes from future
versions of the IETF LSP Ping draft.
Note
We recommend that you use the mpls oam global configuration command instead of the revision option.
Note
If you are running Cisco IOS Release 12.0(27)S1 or Cisco IOS Release 12.0(27)S2, we recommend that
you update to Cisco IOS Release 12.0(27)S3 or a later release. This update ensures that your devices do
not encounter compatibility problems with later Cisco releases that support the ping mpls and trace
mpls commands.
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Note
Cisco implementations Revision 1 and Revision 2 correspond to draft Version 3, but they contain
variations of the TLV encoding. Only Cisco IOS Release 12.0(27)S1 and S2 images encode packets in
Revision 1 format. No images are available on cisco.com to support Revision 2. It is recommended that
you use only images supporting Version 3 and later when configuring TLV encode and decode modes.
MPLS Multipath LSP traceroute requires Cisco Revision 4 or later.
Cisco Vendor Extensions
In Cisco’s Version 3 (draft-ietf-mpls-ping-03.txt) implementations, Cisco defined a vendor extension
TLV in the ignore-if-not-understood TLV space. It is used for the following purposes:
•
Provide an ability to track TLV versions.
•
Provide an experimental Reply TOS capability.
The first capability was defined before the existence of the global configuration command for setting the
echo packet encode and decode behavior. TLV version information in an echo packet overrides the
configured decoding behavior. Using this TLV for TLV versions is no longer required since the
introduction of the global configuration capability.
The second capability controls the reply DSCP. Draft Version 8 defines a Reply TOS TLV, so the use of
the reply DSCP is no longer required.
To enable compatibility between the MPLS LSP and ping or traceroute implementation by customizing
the default behavior of echo packets, perform the following steps.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
mpls oam
4.
echo revision {3 | 4}
5.
echo vendor-extension
6.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Step 3
Command or Action
Purpose
mpls oam
Enter MPLS OAM configuration mode for customizing the
default behavior of echo packets.
Example:
Router(config)# mpls oam
Step 4
echo revision {3 | 4}
Example:
Router(config-mpls)# echo revision 4
Step 5
echo vendor-extension
Specifies the revision number of the echo packet’s default
values.
•
3—draft-ietf-mpls-ping-03 (Revision 2).
•
4—RFC 4379 Compliant (Default).
Sends the Cisco-specific extension of TLVs with echo
packets.
Example:
Router(config-mpls)# echo vendor-extension
Step 6
Returns to global configuration mode.
exit
Example:
Router(config-mpls)# exit
Validating an FEC by Using MPLS LSP Ping and MPLS LSP Traceroute
An LSP is formed by labels. Routers learn labels through LDP, AToM, or some other MPLS applications.
You can use MPLS LSP ping or traceroute to validate an LSP used for forwarding traffic for a given FEC.
This section describes the following tasks:
•
Validating an LDP IPv4 FEC by Using MPLS LSP Ping and MPLS LSP Traceroute, page 12
•
Validating a Layer 2 FEC by Using MPLS LSP Ping and MPLS LSP Traceroute, page 13
Validating an LDP IPv4 FEC by Using MPLS LSP Ping and MPLS LSP Traceroute
To ensure that the router will be able to forward MPLS packets for IPv4 FEC prefixes advertised by LDP,
perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls ipv4 destination-address/destination-mask [exp exp-bits] [repeat count] [verbose]
or
trace mpls ipv4 destination-address/destination-mask
3.
exit
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls ipv4 destination-address
/destination-mask [exp exp-bits] [repeat count]
[verbose]
Selects an LDP IPv4 prefix FEC for validation.
or
trace mpls ipv4 destination-address
/destination-mask
Example:
Router# ping mpls ipv4 10.131.191.252/32 exp 5
repeat 5 verbose
or
Example:
Router# trace mpls ipv4 10.131.191.252/32
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Validating a Layer 2 FEC by Using MPLS LSP Ping and MPLS LSP Traceroute
To ensure that the router will be able to forward MPLS packets for Layer 2 FEC prefixes advertised by
LDP, perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls pseudowire ipv4-address vc-id vc-id
3.
exit
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Enables privileged EXEC mode.
enable
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls pseudowire ipv4-address vc-id vc-id
Selects a Layer 2 FEC for validation.
Example:
Router# ping mpls pseudowire 10.131.191.252
vc-id 333
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Using DSCP to Request a Specific Class of Service in an Echo Reply
For Cisco IOS Release 12.2(27)SXE, Cisco added a reply differentiated services code point (DSCP)
option that lets you request a specific class of service (CoS) in an echo reply.
The reply DSCP option is supported in the experimental mode for IETF draft-ietf-mpls-lsp-ping-03.txt.
Cisco implemented a vendor-specific extension for the reply DSCP option rather than using a Reply TOS
TLV. A Reply TOS TLV serves the same purpose as the reply dscp command in RFC 4379. This draft
provides a standardized method of controlling the reply DSCP.
Note
Before draft Version 8, Cisco implemented the Reply DSCP option as an experimental capability using
a Cisco vendor extension TLV. If a router is configured to encode MPLS echo packets for draft Version 3
implementations, a Cisco vendor extension TLV is used instead of the Reply TOS TLV that was defined
in draft Version 8.
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To use DSCP to request a specific CoS in an echo reply, perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id }
[reply dscp dscp-value]
or
trace mpls ipv4 destination-address/destination-mask [reply dscp dscp-value]
3.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
Controls the DSCP value of an echo reply.
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} [reply dscp dscp-value]
or
trace mpls ipv4 destination-address
/destination-mask [reply dscp dscp-value]
Example:
Router# ping mpls ipv4 10.131.191.252/32 reply
dscp 50
or
Example:
Router# trace mpls ipv4 10.131.191.252/32 reply
dscp 50
Step 3
exit
Returns to user EXEC mode.
Example:
Router# exit
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Controlling How a Responding Router Replies to an MPLS Echo Request
To control how a responding router replies to an MPLS echo request, see the “Reply Modes for an MPLS
LSP Ping and LSP Traceroute Echo Request Response” section.
Reply Modes for an MPLS LSP Ping and LSP Traceroute Echo Request Response
The reply mode controls how a responding router replies to an MPLS echo request sent by a ping mpls
or trace mpls command. There are two reply modes for an echo request packet:
Note
•
ipv4—Reply with an IPv4 UDP packet (default)
•
router-alert—Reply with an IPv4 UDP packet with router alert
It is useful to use ipv4 and router-alert reply modes in conjunction with each other to prevent false
negatives. If you do not receive a reply via the ipv4 mode, it is useful to send a test with the router-alert
reply mode. If both fail, something is wrong in the return path. The problem may be only that the Reply
TOS is not set correctly.
ipv4 Reply Mode
IPv4 packet is the most common reply mode used with a ping mpls or trace mpls command when you
want to periodically poll the integrity of an LSP. With this option, you do not have explicit control over
whether the packet traverses IP or MPLS hops to reach the originator of the MPLS echo request. If the
originating (headend) router fails to receive a reply to an MPLS echo request when you use the reply
mode ipv4 keywords, use the reply mode router-alert keywords.
Router-alert Reply Mode
The router-alert reply mode adds the router alert option to the IP header. When an IP packet that contains
an IP router alert option in its IP header or an MPLS packet with a router alert label as its outermost label
arrives at a router, the router punts (redirects) the packet to the Route Processor (RP) level for handling.
This forces the Cisco router to handle the packet at each intermediate hop as it moves back to the
destination. Hardware and line-card forwarding inconsistencies are bypassed. Router-alert reply mode
is more expensive than IPv4 mode because the reply goes hop-by-hop. It also is slower, so the sender
receives a reply in a relatively longer period of time.
Table 6 describes how IP and MPLS packets with an IP router alert option are handled by the router
switching path processes.
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Table 6
Path Process Handling of IP and MPLS Router Alert Packets
Incoming Packet
Normal Switching Action
Process Switching Action
Outgoing Packet
IP packet—Router alert
option in IP header
Router alert option in IP header
causes the packet to be punted to
the process switching path.
Forwards the packet as is
IP packet—Router alert
option in IP header
Forwards the packet as is
MPLS packet
MPLS packet—
Outermost label contains
a router alert
Removes the outermost router
If the router alert label is the
alert label and forwards the
outermost label, it causes the
packet to be punted to the process packet as an IP packet
switching path.
Preserves the outermost router
alert label and forwards the
MPLS packet
IP packet—Router alert
option in IP header
MPLS packet—
Outermost label contains
a router alert.
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask-length | pseudowire ipv4-address vc-id
vc-id} reply mode {ipv4 | router-alert}
or
trace mpls ipv4 destination-address/destination-mask reply mode {ipv4 | router-alert}
3.
exit
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask-length | pseudowire
ipv4-address vc-id vc-id} reply mode {ipv4 |
router-alert}
or
trace mpls ipv4 destination-address
/destination-mask reply mode {ipv4 |
router-alert}
Checks MPLS LSP connectivity.
or
Discovers MPLS LSP routes that packets actually take
when traveling to their destinations.
Note
To specify the reply mode, you must enter the reply
mode keyword with the ipv4 or router-alert
keyword.
Example:
Router# ping mpls ipv4 10.131.191.252/32 reply
mode ipv4
or
Router# trace mpls ipv4 10.131.191.252/32 reply
mode router-alert
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Preventing Loops when Using MPLS LSP Ping and LSP Traceroute Command
Options
The interaction of the MPLS Embedded Management—LSP Ping for LDP feature options can cause
loops. See the following sections for a description of the loops you may encounter with the ping mpls
and trace mpls commands:
•
Using MPLS LSP Ping to Discover Possible Loops, page 18
•
Using MPLS LSP Traceroute to Discover Possible Loops, page 19
Using MPLS LSP Ping to Discover Possible Loops
With the MPLS LSP Ping feature, loops can occur if you use the UDP destination address range, repeat
option, or sweep option.
To use MPLS LSP ping to discover possible loops, perform the following steps.
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask [destination address-start address-end
increment] | [pseudowire ipv4-address vc-id vc-id address-end increment] } [repeat count] [sweep
minimum maximum size-increment]
3.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask [destination address-start
address-end increment] |[pseudowire
ipv4-address vc-id vc-id address-end
increment]} [repeat count] [sweep minimum
maximum size-increment]
Checks MPLS LSP connectivity.
Example:
Router# ping mpls ipv4 10.131.159.251/32
destination 127.0.0.1 127.0.0.2 1 repeat 2
sweep 1450 1475 25
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Using MPLS LSP Traceroute to Discover Possible Loops
With the MPLS LSP Traceroute feature, loops can occur if you use the UDP destination address range
option and the time-to-live option.
By default, the maximum TTL is set to 30. Therefore, the traceroute output may contain 30 lines if the
target of the traceroute is not reached, which can happen when an LSP problem exists. If an LSP problem
occurs, there may be duplicate entries. The router address of the last point that the trace reaches is
repeated until the output is 30 lines. You can ignore the duplicate entries.
SUMMARY STEPS
1.
enable
2.
trace mpls ipv4 destination-address/destination-mask [destination address-start address-end
address-increment] [ttl maximum-time-to-live]
3.
exit
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
trace mpls ipv4 destination-address
/destination-mask [destination address-start
address-end address increment] [ttl
maximum-time-to-live]
Discovers MPLS LSP routes that packets take when
traveling to their destinations. The example shows how a
loop can occur.
Example:
Router# trace mpls ipv4 10.131.159.251/32
destination 127.0.0.1 127.0.0.3 1 ttl 5
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Detecting LSP Breaks
If there is a problem forwarding MPLS packets in your network, you can determine where there are LSP
breaks. This section describes the following concepts:
•
MPLS Echo Request Packets Not Forwarded by IP, page 20
•
MTU Discovery in an LSP, page 21
MPLS Echo Request Packets Not Forwarded by IP
MPLS echo request packets sent during an LSP ping are never forwarded by IP. The IP header destination
address field in an MPLS echo request packet is a 127.x.y.z/8 address. Routers should not forward
packets using a 127.x.y.z/8 address. The 127.x.y.z/8 address corresponds to an address for the local host.
Use of a 127.x.y.z address as the destination address of the UDP packet is significant because the MPLS
echo request packet fails to make it to the target router if a transit router does not label switch the LSP.
The use of the 127.x.y.z address allows for the detection of LSP breakages. The following occurs at the
transit router:
•
If an LSP breakage occurs at a transit router, the MPLS echo packet is not forwarded; it is consumed
by the router.
•
If the LSP is intact, the MPLS echo packet reaches the target router and is processed by the terminal
point of the LSP.
Figure 3 shows the path of the MPLS echo request and reply when a transit router fails to label switch a
packet in an LSP.
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Figure 3
Path when Transit Router Fails to Label Switch a Packet
103389
LSP breakage
MPLS echo
request
PE1
PE2
Target router
MPLS echo reply
Note
An AToM payload does not contain usable forwarding information at a transit router because the payload
may not be an IP packet. An MPLS VPN packet, although an IP packet, does not contain usable
forwarding information at a transit router because the destination IP address is significant only to the
Virtual Routing and Forwarding (VRF) instances at the endpoints of the MPLS network.
MTU Discovery in an LSP
Untagged output interfaces at a penultimate hop do not impact the forwarding of IP packets through an
LSP because the forwarding decision is made at the penultimate hop through use of the incoming label.
However, untagged output interfaces cause AToM and MPLS VPN traffic to be dropped at the
penultimate hop.
During an MPLS LSP ping, MPLS echo request packets are sent with the IP packet attribute set to “do
not fragment.” That is, the Don’t Fragment (DF) bit is set in the IP header of the packet. This allows you
to use the MPLS echo request to test for the MTU that can be supported for the packet through the LSP
without fragmentation.
Figure 4 shows a sample network with a single LSP from PE1 to PE2 formed with labels advertised by
the LDP.
Sample Network with LSP—Labels Advertised by LDP
10.131.191.253 10.131.191.252
E2/0
E2/0
CE1 10.0.0.1
10.131.191.251
E0/0
E1/0
E0/0
PE1
10.131.159.251
E1/0
P1
10.131.159.252
E0/0
E0/0
P2
PE2
10.131.159.253
E2/0
E2/0
10.0.0.2 CE2
103390
Figure 4
You can determine the maximum receive unit (MRU) at each hop by using the MPLS Traceroute feature
to trace the LSP. The MRU is the maximum size of a labeled packet that can be forwarded through an
LSP.
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This section contains the following tasks:
•
Tracking Packets Tagged as Implicit Null, page 22
•
Tracking Untagged Packets, page 23
•
Determining Why a Packet Could Not Be Sent, page 23
•
Detecting LSP Breaks when Load Balancing Is Enabled for IPv4 LDP LSPs, page 24
•
Specifying the Interface Through Which Echo Packets Leave a Router, page 25
•
Pacing the Transmission of Packets, page 27
•
Interrogating the Transit Router for Its Downstream Information by Using Echo Request
request-dsmap, page 28
•
Interrogating a Router for Its DSMAP, page 29
•
Requesting that a Transit Router Validate the Target FEC Stack, page 30
•
Enabling LSP Ping to Detect LSP Breakages Caused by Untagged Interfaces, page 31
•
Verifying the AToM VCCV Capabilities Advertised to and Received from the Peer, page 32
Tracking Packets Tagged as Implicit Null
To track packets tagged as implicit null, perform the following steps.
SUMMARY STEPS
1.
enable
2.
trace mpls ipv4 destination-address /destination-mask
3.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
trace mpls ipv4 destination-address
/destination-mask
Discovers MPLS LSP routes that packets actually take
when traveling to their destinations.
Example:
Router# trace mpls ipv4 10.131.159.252/32
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Tracking Untagged Packets
To track untagged packets, perform the following steps.
SUMMARY STEPS
1.
enable
2.
show mpls forwarding-table destination-address/destination-mask
3.
show mpls ldp discovery
4.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
show mpls forwarding-table
destination-address/destination-mask
Displays the content of the MPLS Label Forwarding
Information Base (LFIB) and displays whether the LDP is
properly configured.
Example:
Router# show mpls forwarding-table
10.131.159.252/32
Step 3
show mpls ldp discovery
Displays the status of the LDP discovery process and
displays whether the LDP is properly configured.
Example:
Router# show mpls ldp discovery
Step 4
Returns to user EXEC mode.
exit
Example:
Router# exit
Determining Why a Packet Could Not Be Sent
The Q return code means that the packet could not be sent. The problem can be caused by insufficient
processing memory, but it probably results because an LSP could not be found that matches the FEC
information that was entered on the command line.
You need to determine the reason why the packet was not forwarded so that you can fix the problem in
the path of the LSP. To do so, look at the Routing Information Base (RIB), the Forwarding Information
Base (FIB), the Label Information Base (LIB), and the MPLS LFIB. If there is no entry for the FEC in
any of these routing or forwarding bases, there is a Q return code.
To determine why a packet could not be transmitted, perform the following steps.
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
SUMMARY STEPS
1.
enable
2.
show ip route [ip-address [mask] ]
3.
show mpls forwarding-table [network {mask | length} | labels label [- label] | interface interface
| next-hop address | lsp-tunnel [tunnel-id]]
4.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
show ip route [ip-address [mask]]
Displays the current state of the routing table.
Example:
When the MPLS echo reply returns a Q, troubleshooting
occurs on the routing information database.
Router# show ip route 10.0.0.1
Step 3
show mpls forwarding-table [network {mask |
length} | labels label [-label] | interface
interface | next-hop address | lsp-tunnel
[tunnel-id]]
Displays the content of the MPLS LFIB. When the MPLS
echo reply returns a Q, troubleshooting occurs on a label
information database and an MPLS forwarding information
database.
Example:
Router# show mpls forwarding-table 10.0.0.1/32
Step 4
Returns to user EXEC mode.
exit
Example:
Router# exit
Detecting LSP Breaks when Load Balancing Is Enabled for IPv4 LDP LSPs
An ICMP ping or trace follows one path from the originating router to the target router. Round robin load
balancing of IP packets from a source router discovers the various output paths to the target IP address.
For MPLS ping and traceroute, Cisco routers use the source and destination addresses in the IP header
for load balancing when multiple paths exist through the network to a target router. The Cisco
implementation of MPLS may check the destination address of an IP payload to accomplish load
balancing (the type of checking depends on the platform).
To detect LSP breaks when load balancing is enabled for IPv4 LDP LSPs, perform the following steps.
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
SUMMARY STEPS
1.
enable
2.
ping mpls ipv4 destination-address/destination-mask-length [destination address-start
address-end increment]
3.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls ipv4 destination-address
/destination-mask-length [destination
address-start address-end increment]
Checks for load balancing paths.
Enter the 127.z.y.x/8 destination address.
Example:
Router# ping mpls ipv4 10.131.159.251/32
destination 127.0.0.1/8
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Specifying the Interface Through Which Echo Packets Leave a Router
To specify the interface through which echo packets leave a router, perform the following steps.
Echo Request Output Interface Control
You can control the interface through which packets leave a router. Path output information is used as
input to LSP ping and traceroute.
The echo request output interface control feature allows you to force echo packets through the paths that
perform detailed debugging or characterizing of the LSP. This feature is useful if a PE router connects
to an MPLS cloud and there are broken links. You can direct traffic through a certain link. The feature
also is helpful for troubleshooting network problems.
To specify the output interface for echo requests, perform the following steps.
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id}
[output interface tx-interface]
or
trace mpls ipv4 destination-address/destination-mask [output interface tx-interface]
3.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} [output interface tx-interface]
Checks MPLS LSP connectivity.
or
or
Discovers MPLS LSP routes that packets actually take
when traveling to their destinations.
trace mpls ipv4
destination-address/destination-mask [output
interface tx-interface]
Note
You must specify the output interface keyword.
Example:
Router# ping mpls ipv4 10.131.159.251/32 output
interface ethernet0/0
or
Router# trace mpls ipv4 10.131.159.251/32
output interface ethernet0/0
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
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How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Pacing the Transmission of Packets
Echo request traffic pacing allows you to pace the transmission of packets so that the receiving router
does not drop packets. To perform echo request traffic pacing, perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id}
[interval ms]
or
trace mpls ipv4 destination-address/destination-mask
3.
exit
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} [interval ms]
Checks MPLS LSP connectivity.
or
or
Discovers MPLS LSP routes that packets take when
traveling to their destinations.
trace mpls ipv4 destination-address
/destination-mask
Note
In the ping mpls command, you must specify the
interval keyword.
Example:
Router# ping mpls ipv4 10.131.159.251/32
interval 2
or
Example:
Router# trace mpls ipv4 10.131.159.251/32
Step 3
exit
Returns to user EXEC mode.
Example:
Router# exit
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
27
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Interrogating the Transit Router for Its Downstream Information by Using Echo Request
request-dsmap
The echo request request-dsmap capability troubleshooting feature, used in conjunction with the TTL
flag, allows you to selectively interrogate a transit router. If there is a failure, you do not have to enter
an lsp traceroute command for each previous failure; you can focus just on the failed hop.
A request-dsmap flag in the downstream mapping flags field, and procedures that specify how to trace
noncompliant routers allow you to arbitrarily time-to-live (TTL) expire MPLS echo request packets with
a wildcard downstream map (DSMAP).
Echo request DSMAPs received without labels indicate that the sender did not have any DSMAPs to
validate. If the downstream router ID field of the DSMAP TLV in an echo request is set to the
ALLROUTERs address (224.0.0.2) and there are no labels, the source router can arbitrarily query a
transit router for its DSMAP information.
The ping mpls command allows an MPLS echo request to be TTL-expired at a transit router with a
wildcard DSMAP for the explicit purpose of troubleshooting and querying the downstream router for its
DSMAPs. The default is that the DSMAP has an IPv4 bitmap hashkey. You also can select hashkey 0
(none). The purpose of the ping mpls command is to allow the source router to selectively TTL expire
an echo request at a transit router to interrogate the transit router for its downstream information. The
ability to also select a multipath (hashkey) type allows the transmitting router to interrogate a transit
router for load-balancing information as is done with multipath LSP traceroute, but without having to
interrogate all subsequent nodes traversed between the source router and the router on which each echo
request TTL expires. Use an echo request in conjunction with the TTL setting because if an echo request
arrives at the egress of the LSP with an echo request, the responding routers never return DSMAPs.
To interrogate the transit router for its downstream information so that you can focus just on the failed
hop if there is a failure, perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id}
[dsmap [hashkey {none | ipv4 bitmap bitmap-size}]]
3.
exit
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
28
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} [dsmap [hashkey {none | ipv4
bitmap bitmap-size}]]
Checks MPLS LSP connectivity.
Note
You must specify the dsmap and hashkey
keywords.
Example:
Router# ping mpls ipv4 10.161.251/32 dsmap
hashkey ipv4 bitmap 16
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Interrogating a Router for Its DSMAP
The router can interrogate the software or hardware forwarding layer for the depth limit that needs to be
returned in the DSMAP TLV. If forwarding does not provide a value, the default is 255.
To determine the depth limit, specify the dsmap and ttl keywords in the ping mpls command. The transit
router will be interrogated for its DSMAP. The depth limit is returned with the echo reply DSMAP. A
value of 0 means that the IP header is used for load balancing. Another value indicates that the IP header
load balances up to the specified number of labels.
To interrogate a router for its DSMAP, perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id} ttl
time-to-live dsmap
3.
exit
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
29
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} ttl time-to-live dsmap
Checks MPLS LSP connectivity.
Note
You must specify the ttl and dsmap keywords.
Example:
Router# ping mpls ipv4 10.131.159.252/32 ttl 1
dsmap
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Requesting that a Transit Router Validate the Target FEC Stack
An MPLS echo request tests a particular LSP. The LSP to be tested is identified by the FEC stack.
To request that a transit router validate the target FEC stack, set the V flag from the source router by
entering the flags fec keyword in the ping mpls and trace mpls commands. The default is that echo
request packets are sent with the V flag set to 0.
To request that a transit router validate the target FEC stack, perform the following steps.
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id}
flags fec
or
trace mpls ipv4 destination-address/destination-mask flags fec
3.
exit
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
Checks MPLS LSP connectivity.
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} flags fec
or
or
Discovers MPLS LSP routes that packets actually take
when traveling to their destinations.
trace mpls ipv4 destination-address
/destination-mask flags fec
Note
You must enter the flags fec keyword.
Example:
Router# ping mpls ipv4 10.131.159.252/32 flags
fec
or
Example:
Router# trace mpls ipv4 10.131.159.252/32 flags
fec
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Enabling LSP Ping to Detect LSP Breakages Caused by Untagged Interfaces
For MPLS LSP ping and traceroute of LSPs carrying IPv4 FECs, you can force an explicit null label to
be added to the MPLS label stack even though the label was unsolicited. This allows LSP ping to detect
LSP breakages caused by untagged interfaces. LSP ping does not report that an LSP is fine when it is
unable to send MPLS traffic.
An explicit null label is added to an MPLS label stack if MPLS echo request packets are forwarded from
untagged interfaces that are directly connected to the destination of the LSP ping or if the IP TTL value
for the MPLS echo request packets is set to 1.
When you enter an lsp ping command, you are testing the LSP’s ability to carry IP traffic. Failure at
untagged output interfaces at the penultimate hop are not detected. Explicit-null shimming allows you
to test an LSP’s ability to carry MPLS traffic.
To enable LSP ping to detect LSP breakages caused by untagged interfaces, specify the
force-explicit-null keyword in the ping mpls or trace mpls commands as shown in the following steps.
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31
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
How to Configure MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
SUMMARY STEPS
1.
enable
2.
ping mpls {ipv4 destination-address/destination-mask | pseudowire ipv4-address vc-id vc-id}
force-explicit-null
or
trace mpls ipv4 destination-address/destination-mask force-explicit-null
3.
exit
DETAILED STEP
Step 1
Enables privileged EXEC mode.
enable
•
Enter your password if prompted.
Example:
Router> enable
Step 2
ping mpls {ipv4 destination-address
/destination-mask | pseudowire ipv4-address
vc-id vc-id} force-explicit-null
Checks MPLS LSP connectivity.
or
or
Discovers MPLS LSP routes that packets actually take
when traveling to their destinations.
trace mpls ipv4 destination-address
/destination-mask force-explicit-null
Note
You must enter the force-explicit-null keyword.
Example:
Router# ping mpls ipv4 10.131.191.252/32
force-explicit null
or
Example:
Router# trace mpls ipv4 10.131.191.252/32
65force-explicit-null
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Verifying the AToM VCCV Capabilities Advertised to and Received from the Peer
To verify the AToM VCCV capabilities advertised to and received from the peer, perform the following
steps.
SUMMARY STEPS
1.
enable
2.
show mpls l2transport binding
3.
exit
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32
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Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
DETAILED STEPS
Step 1
Enables privileged EXEC mode.
enable
•
Enter your password if prompted.
Example:
Router> enable
Step 2
Displays VC label binding information.
show mpls l2transport binding
Example:
Router# show mpls l2transport binding
Step 3
Returns to user EXEC mode.
exit
Example:
Router# exit
Configuration Examples for MPLS LSP Ping/Traceroute for
LDP/TE, and LSP Ping for VCCV
Examples for the MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV feature are based
on the sample topology shown in Figure 5.
Figure 5
Sample Topology for Configuration Examples
10.131.191.253
10.131.191.252 10.131.191.251
E0/0
E2/0
CE1 10.0.0.1
E1/0 E1/0
E1/1 E1/1
E0/0
PE1
P1
LSP
E0/0 E0/0
E0/1 E0/1
P2
E2/0
E2/0
PE2
10.0.0.2 CE2
103392
E2/0
10.131.159.251 10.131.159.252 10.131.159.253
This section contains the following configuration examples:
•
Enabling Compatibility Between the MPLS LSP and Ping or Traceroute Implementation: Example,
page 34
•
Validating an FEC by Using MPLS LSP Ping and LSP Traceroute: Example, page 34
•
Using DSCP to Request a Specific Class of Service in an Echo Reply: Example, page 35
•
Preventing Loops when Using MPLS LSP Ping and LSP Traceroute Command Options: Example,
page 35
•
Detecting LSP Breaks: Example, page 39
•
Verifying the AToM VCCV Capabilities Advertised to and Received from the Peer: Example,
page 60
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33
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Enabling Compatibility Between the MPLS LSP and Ping or Traceroute
Implementation: Example
The following example shows how to configure MPLS multipath LSP traceroute to interoperate with a
vendor implementation that does not interpret RFC 4379 as Cisco does:
configure terminal
!
mpls oam
echo revision 4
no echo vendor-extension
exit
The default echo revision number is 4, which corresponds to the IEFT draft 11.
Validating an FEC by Using MPLS LSP Ping and LSP Traceroute: Example
This section describes the following procedures:
•
Validating an LDP IPv4 FEC by Using MPLS LSP Ping and MPLS LSP Traceroute: Example,
page 34
•
Validating a Layer 2 FEC by Using MPLS LSP Ping: Example, page 34
Validating an LDP IPv4 FEC by Using MPLS LSP Ping and MPLS LSP Traceroute: Example
The following example shows how to use the ping mpls command to test connectivity of an
IPv4 LDP LSP:
Router# ping mpls ipv4 10.131.191.252/32 exp 5 repeat 5 verbose
Sending 5, 100-byte MPLS Echos to 10.131.191.252, timeout is 2 seconds:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
10.131.191.230, return code
!
10.131.191.230, return code
!
10.131.191.230, return code
!
10.131.191.230, return code
!
10.131.191.230, return code
3
3
3
3
3
Success rate is 100 percent (5/5), round-trip min/avg/max = 100/10
Validating a Layer 2 FEC by Using MPLS LSP Ping: Example
The following example validates a Layer 2 FEC:
Router# ping mpls pseudowire 10.10.10.15 108 vc-id 333
Sending 5, 100-byte MPLS Echos to 10.10.10.15,
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
34
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
timeout is 2 seconds, send interval is 0 msec:
Codes:
'L'
'D'
'M'
'P'
'R'
'X'
'!' - success, 'Q' - request not sent, '.' - timeout,
- labeled output interface, 'B' - unlabeled output interface,
- DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
- malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
- no rx intf label prot, 'p' - premature termination of LSP,
- transit router, 'I' - unknown upstream index,
- unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/32/40 ms PE-802#
Using DSCP to Request a Specific Class of Service in an Echo Reply: Example
The following example shows how to use DSCP to request a specific CoS in an echo reply:
Router# ping mpls ipv4 10.131.159.252/32 reply dscp 50
<0-63>
af11
af12
af13
af21
af22
af23
af31
af32
af33
af41
af42
af43
cs1
cs2
cs3
cs4
cs5
cs6
cs7
default
ef
Differentiated services codepoint value
Match packets with AF11 dscp (001010)
Match packets with AF12 dscp (001100)
Match packets with AF13 dscp (001110)
Match packets with AF21 dscp (010010)
Match packets with AF22 dscp (010100)
Match packets with AF23 dscp (010110)
Match packets with AF31 dscp (011010)
Match packets with AF32 dscp (011100)
Match packets with AF33 dscp (011110)
Match packets with AF41 dscp (100010)
Match packets with AF42 dscp (100100)
Match packets with AF43 dscp (100110)
Match packets with CS1(precedence 1) dscp
Match packets with CS2(precedence 2) dscp
Match packets with CS3(precedence 3) dscp
Match packets with CS4(precedence 4) dscp
Match packets with CS5(precedence 5) dscp
Match packets with CS6(precedence 6) dscp
Match packets with CS7(precedence 7) dscp
Match packets with default dscp (000000)
Match packets with EF dscp (101110)
(001000)
(010000)
(011000)
(100000)
(101000)
(110000)
(111000)
Preventing Loops when Using MPLS LSP Ping and LSP Traceroute Command
Options: Example
This section contains the following examples:
•
Possible Loops with MPLS LSP Ping: Example, page 35
•
Possible Loop with MPLS LSP Traceroute: Example, page 37
Possible Loops with MPLS LSP Ping: Example
The following example shows how a loop operates if you use the following ping mpls command:
Router# ping mpls ipv4 10.131.159.251/32 destination 127.0.0.1 127.0.0.2 1 repeat 2
sweep 1450 1475 25
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35
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Sending 2, [1450..1500]-byte MPLS Echos to 10.131.159.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
Destination address 127.0.0.1
!
!
Destination address 127.0.0.2
!
!
Destination address 127.0.0.1
!
!
Destination address 127.0.0.2
!
!
A ping mpls command is sent for each packet size range for each destination address until the end
address is reached. For this example, the loop continues in the same manner until the destination address,
127.0.0.5, is reached. The sequence continues until the number is reached that you specified with the
repeat count keyword and argument. For this example, the repeat count is 2. The MPLS LSP ping loop
sequence is as follows:
repeat = 1
destination address 1 (address-start)
for (size from sweep minimum to maximum, counting by size-increment)
send an lsp ping
destination address 2 (address-start + address-increment)
for (size from sweep minimum to maximum, counting by size-increment)
send an lsp ping
destination address 3 (address-start + address-increment + address-increment)
for (size from sweep minimum to maximum, counting by size-increment)
send an lsp ping
.
.
.
until destination address = address-end
.
.
.
until repeat = count 2
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36
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Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Possible Loop with MPLS LSP Traceroute: Example
The following example shows how a loop occurs if you use the following trace mpls command:
Router# trace mpls ipv4 10.131.159.251/32 destination 127.0.0.1 127.0.0.3 1 ttl 5
Tracing MPLS Label Switched Path to 10.131.159.251/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
Destination address 127.0.0.1
0 10.131.191.230 MRU 1500 [Labels: 19 Exp: 0]
R 1 10.131.159.226 MRU 1504 [implicit-null] 40 ms
! 2 10.131.159.225 40 ms
Destination address 127.0.0.2
0 10.131.191.230 MRU 1500 [Labels: 19 Exp: 0]
R 1 10.131.159.226 MRU 1504 [implicit-null] 40 ms
! 2 10.131.159.225 40 ms
Destination address 127.0.0.3
0 10.131.191.230 MRU 1500 [Labels: 19 Exp: 0]
R 1 10.131.159.226 MRU 1504 [implicit-null] 40 ms
! 2 10.131.159.225 48 ms
An mpls trace command is sent for each TTL from 1 to the maximum TTL (ttl maximum-time-to-live
keyword and argument) for each destination address until the address specified with the destination
end-address argument is reached. In this example, the maximum TTL is 5 and the end destination
address is 127.0.0.3. The MPLS LSP traceroute loop sequence is as follows:
destination address 1 (address-start)
for (ttl from 1 to maximum-time-to-live)
send an lsp trace
destination address 2 (address-start + address-increment)
for (ttl from 1 to 5)
send an lsp trace
destination address 3 (address-start + address-increment + address-increment)
for (ttl from 1 to maximum-time-to-live)
send an lsp trace
.
.
.
until destination address = 4
The following example shows that the trace encountered an LSP problem at the router that has an IP
address of 10.6.1.6:
Router# traceroute mpls ipv4 10.6.7.4/32
Tracing MPLS Label Switched Path to 10.6.7.4/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
37
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.6.1.14 MRU 4470 [Labels: 22 Exp: 0]
R 1 10.6.1.5 MRU 4470 [Labels: 21 Exp: 0] 2 ms
R 2 10.6.1.6 4 ms
<------ Router address repeated for 2nd to 30th TTL.
R 3 10.6.1.6 1 ms
R 4 10.6.1.6 1 ms
R 5 10.6.1.6 3 ms
R 6 10.6.1.6 4 ms
R 7 10.6.1.6 1 ms
R 8 10.6.1.6 2 ms
R 9 10.6.1.6 3 ms
R 10 10.6.1.6 4 ms
R 11 10.6.1.6 1 ms
R 12 10.6.1.6 2 ms
R 13 10.6.1.6 4 ms
R 14 10.6.1.6 5 ms
R 15 10.6.1.6 2 ms
R 16 10.6.1.6 3 ms
R 17 10.6.1.6 4 ms
R 18 10.6.1.6 2 ms
R 19 10.6.1.6 3 ms
R 20 10.6.1.6 4 ms
R 21 10.6.1.6 1 ms
R 22 10.6.1.6 2 ms
R 23 10.6.1.6 3 ms
R 24 10.6.1.6 4 ms
R 25 10.6.1.6 1 ms
R 26 10.6.1.6 3 ms
R 27 10.6.1.6 4 ms
R 28 10.6.1.6 1 ms
R 29 10.6.1.6 2 ms
R 30 10.6.1.6 3 ms
<------ TTL 30.
If you know the maximum number of hops in your network, you can set the TTL to a lower value with
the trace mpls ttl maximum-time-to-live command. The following example shows the same traceroute
command as the previous example, except that this time the TTL is set to 5:
Router# traceroute mpls ipv4 10.6.7.4/32 ttl 5
Tracing MPLS Label Switched Path to 10.6.7.4/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.6.1.14 MRU 4470 [Labels: 22 Exp: 0]
R 1 10.6.1.5 MRU 4474 [No Label] 3 ms
R 2 10.6.1.6 4 ms
<------ Router address repeated for 2nd to 5th TTL.
R 3 10.6.1.6 1 ms
R 4 10.6.1.6 3 ms
R 5 10.6.1.6 4 ms
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
38
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Detecting LSP Breaks: Example
This section contains the following examples:
•
Troubleshooting with LSP Ping or Traceroute: Example, page 39
•
MTU Discovery in an LSP: Example, page 49
•
Tracking Packets Tagged as Implicit Null: Example, page 50
•
Tracking Untagged Packets: Example, page 51
•
Determining Why a Packet Could Not Be Sent: Example, page 52
•
Detecting LSP Breaks when Load Balancing Is Enabled for IPv4 LSPs: Example, page 53
•
Specifying the Interface Through Which Echo Packets Leave a Router: Example, page 54
•
Pacing the Transmission of Packets: Example, page 56
•
Interrogating the Transit Router for Its Downstream Information: Example, page 56
•
Interrogating a Router for Its DSMAP: Example, page 58
•
Requesting that a Transit Router Validate the Target FEC Stack: Example, page 58
•
Enabling LSP Ping to Detect LSP Breakages Caused by Untagged Interfaces: Example, page 59
Troubleshooting with LSP Ping or Traceroute: Example
ICMP ping and trace commands are often used to help diagnose the root cause of a failure. When an
LSP is broken, the packet may reach the target router by IP forwarding, thus making the ICMP ping and
traceroute features unreliable for detecting MPLS forwarding problems. The MPLS LSP ping or
traceroute and AToM VCCV features extend this diagnostic and troubleshooting ability to the MPLS
network and handle inconsistencies (if any) between the IP and MPLS forwarding tables, inconsistencies
in the MPLS control and data plane, and problems with the reply path.
Figure 6 shows a sample topology with an LDP LSP.
Sample Topology with LDP LSP
10.131.191.253 10.131.191.252
E2/0
E2/0
CE1 10.0.0.1
PE1
E1/0
10.131.191.251
E0/0
10.131.159.251 10.131.159.252
E1/0
E0/0
E0/0
E1/0
E0/0
P1
P2
10.131.159.253
E2/0
E2/0
10.0.0.2 CE2
PE2
E1/0
This section contains the following subsections:
•
Configuration for Sample Topology, page 40
•
Verification That the LSP Is Set Up Correctly, page 46
•
Discovery of LSP Breaks, page 47
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
39
103391
Figure 6
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration for Sample Topology
These are sample topology configurations for the troubleshooting examples in the following sections
(see Figure 6). There are the six sample router configurations.
Router CE1 Configuration
Following is the configuration for the CE1 router:
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CE1
!
boot-start-marker
boot-end-marker
!
enable password lab
!
clock timezone EST -5
ip subnet-zero
!
!
!
interface Loopback0
ip address 10.131.191.253 255.255.255.255
no ip directed-broadcast
no clns route-cache
!
!
interface Ethernet2/0
no ip address
no ip directed-broadcast
no keepalive
no cdp enable
no clns route-cache
!
interface Ethernet2/0.1
encapsulation dot1Q 1000
ip address 10.0.0.1 255.255.255.0
no ip directed-broadcast
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
exec-timeout 0 0
password lab
login
!
end
Router PE1 Configuration
Following is the configuration for the PE1 router:
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
40
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
no service password-encryption
!
hostname PE1
!
boot-start-marker
boot-end-marker
!
logging snmp-authfail
enable password lab
!
clock timezone EST -5
ip subnet-zero
ip cef
no ip domain-lookup
!
mpls ldp discovery targeted-hello accept
mpls ldp router-id Loopback0 force
mpls label protocol ldp
!
!
!
interface Loopback0
ip address 10.131.191.252 255.255.255.255
no clns route-cache
!
interface Ethernet0/0
ip address 10.131.191.230 255.255.255.252
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet1/0
ip address 10.131.159.246 255.255.255.252
shutdown
no clns route-cache
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet2/0
no ip address
no cdp enable
no clns route-cache
!
interface Ethernet2/0.1
encapsulation dot1Q 1000
xconnect 10.131.159.252 333 encapsulation mpls
!
!
router ospf 1
log-adjacency-changes
passive-interface Loopback0
network 10.131.159.244 0.0.0.3 area 0
network 10.131.191.228 0.0.0.3 area 0
network 10.131.191.232 0.0.0.3 area 0
network 10.131.191.252 0.0.0.0 area 0
!
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
exec-timeout 0 0
password lab
login
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
41
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
!
!
end
Router P1 Configuration
Following is the configuration for the P1 router:
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname P1
!
boot-start-marker
boot-end-marker
!
logging snmp-authfail
enable password lab
!
clock timezone EST -5
ip subnet-zero
ip cef
no ip domain-lookup
!
!
mpls ldp discovery targeted-hello accept
mpls ldp router-id Loopback0 force
mpls label protocol ldp
!
!
!
no clns route-cache
!
interface Loopback0
ip address 10.131.191.251 255.255.255.255
no clns route-cache
!
interface Ethernet0/0
ip address 10.131.191.229 255.255.255.252
no clns route-cache
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet1/0
ip address 10.131.159.226 255.255.255.252
no clns route-cache
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet1/1
ip address 10.131.159.222 255.255.255.252
no clns route-cache
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
!
router ospf 1
log-adjacency-changes
passive-interface Loopback0
network 10.131.159.220 0.0.0.3 area 0
network 10.131.159.224 0.0.0.3 area 0
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42
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
network 10.131.191.228 0.0.0.3 area 0
network 10.131.191.251 0.0.0.0 area 0
mpls traffic-eng router-id Loopback0
mpls traffic-eng area 0
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
exec-timeout 0 0
password lab
login
!
end
Router P2 Configuration
Following is the configuration for the P2 router:
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname P2
!
boot-start-marker
boot-end-marker
!
enable password lab
!
clock timezone EST -5
ip subnet-zero
ip cef
no ip domain-lookup
!
mpls ldp discovery targeted-hello accept
mpls ldp router-id Loopback0 force
mpls label protocol ldp
!
!
!
interface Loopback0
ip address 10.131.159.251 255.255.255.255
no ip directed-broadcast
!
interface Ethernet0/0
ip address 10.131.159.229 255.255.255.252
no ip directed-broadcast
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet0/1
ip address 10.131.159.233 255.255.255.252
no ip directed-broadcast
ip rsvp signalling dscp 0
!
interface Ethernet1/0
ip address 10.131.159.225 255.255.255.252
no ip directed-broadcast
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
43
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
!
interface Ethernet1/1
ip address 10.131.159.221 255.255.255.252
no ip directed-broadcast
ip rsvp signalling dscp 0
!
!
router ospf 1
log-adjacency-changes
passive-interface Loopback0
network 10.131.159.220 0.0.0.3 area 0
network 10.131.159.224 0.0.0.3 area 0
network 10.131.159.228 0.0.0.3 area 0
network 10.131.159.232 0.0.0.3 area 0
network 10.131.159.251 0.0.0.0 area 0
!
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
exec-timeout 0 0
password lab
login
!
end
Router PE2 Configuration
Following is the configuration for the PE2 router:
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname PE2
!
boot-start-marker
boot-end-marker
!
logging snmp-authfail
enable password lab
!
clock timezone EST -5
ip subnet-zero
ip cef
no ip domain-lookup
!
mpls ldp discovery targeted-hello accept
mpls ldp router-id Loopback0 force
mpls label protocol ldp
!
!
!
interface Loopback0
ip address 10.131.159.252 255.255.255.255
no clns route-cache
!
interface Ethernet0/0
ip address 10.131.159.230 255.255.255.252
no clns route-cache
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet0/1
ip address 10.131.159.234 255.255.255.252
no clns route-cache
ip rsvp bandwidth 1500 1500
ip rsvp signalling dscp 0
!
interface Ethernet1/0
ip address 10.131.159.245 255.255.255.252
mpls ip
no clns route-cache
!
interface Ethernet3/0
no ip address
no cdp enable
no clns route-cache
!
interface Ethernet3/0.1
encapsulation dot1Q 1000
no snmp trap link-status
no cdp enable
xconnect 10.131.191.252 333 encapsulation mpls
!
!
router ospf 1
log-adjacency-changes
passive-interface Loopback0
network 10.131.122.0 0.0.0.3 area 0
network 10.131.159.228 0.0.0.3 area 0
network 10.131.159.232 0.0.0.3 area 0
network 10.131.159.236 0.0.0.3 area 0
network 10.131.159.244 0.0.0.3 area 0
network 10.131.159.252 0.0.0.0 area 0
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
exec-timeout 0 0
password lab
login
!
!
end
Router CE2 Configuration
Following is the configuration for the CE2 router:
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CE2
!
boot-start-marker
boot-end-marker
!
enable password lab
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
45
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
!
clock timezone EST -5
ip subnet-zero
ip cef
no ip domain-lookup
!
!
interface Loopback0
ip address 10.131.159.253 255.255.255.255
no ip directed-broadcast
no clns route-cache
!
interface Ethernet3/0
no ip address
no ip directed-broadcast
no keepalive
no cdp enable
no clns route-cache
!
interface Ethernet3/0.1
encapsulation dot1Q 1000
ip address 10.0.0.2 255.255.255.0
no ip directed-broadcast
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
exec-timeout 0 0
password lab
login
!
end
Verification That the LSP Is Set Up Correctly
Use the output from the show commands in this section to verify that the LSP is configured correctly.
A show mpls forwarding-table command shows that tunnel 1 is in the MPLS forwarding table.
PE1# show mpls forwarding-table 10.131.159.252
Local
tag
22
[T]
Outgoing
Prefix
tag or VC
or Tunnel Id
18 [T] 10.131.159.252/32 0
Bytes tag
switched
Tu1
Outgoing
Next Hop
interface
point2point
Forwarding through a TSP tunnel.
View additional tagging info with the 'detail' option
A trace mpls command issued at PE1 verifies that packets with 16 as the outermost label and 18 as the
end-of-stack label are forwarded from PE1 to PE2.
PE1# trace mpls ipv4 10.131.159.252/32
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
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46
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.252 MRU 1496 [Labels: 16/18 Exp: 0/0] L 1 10.131.191.229
MRU 1508 [Labels: 18 Exp: 0] 0 ms L 2 10.131.159.225
MRU 1504 [Labels: implicit-null Exp: 0] 0 ms ! 3 10.131.159.234 20 ms
PE1#
The MPLS LSP Traceroute to PE2 is successful, as indicated by the exclamation point (!).
Discovery of LSP Breaks
Use the output of the commands in this section to discover LSP breaks.
An LDP target session is established between routers PE1 and P2, as shown in the output of the following
show mpls ldp discovery command:
PE1# show mpls ldp discovery
Local LDP Identifier:
10.131.191.252:0
Discovery Sources:
Interfaces:
Ethernet0/0 (ldp): xmit/recv
LDP Id: 10.131.191.251:0
Tunnel1 (ldp): Targeted -> 10.131.159.251
Targeted Hellos:
10.131.191.252 -> 10.131.159.252 (ldp): active/passive, xmit/recv
LDP Id: 10.131.159.252:0
10.131.191.252 -> 10.131.159.251 (ldp): active, xmit/recv
LDP Id: 10.131.159.251:0
Enter the following command on the P2 router in global configuration mode:
P2(config)# no mpls ldp discovery targeted-hello accept
The LDP configuration change causes the targeted LDP session between the headend and tailend of the
TE tunnel to go down. Labels for IPv4 prefixes learned by P2 are not advertised to PE1. Thus, all IP
prefixes reachable by P2 are reachable by PE1 only through IP (not MPLS). In other words, packets
destined for those prefixes through Tunnel 1 at PE1 will be IP switched at P2 (which is undesirable).
The following show mpls ldp discovery command shows that the LDP targeted session is down:
PE1# show mpls ldp discovery
Local LDP Identifier:
10.131.191.252:0
Discovery Sources:
Interfaces:
Ethernet0/0 (ldp): xmit/recv
LDP Id: 10.131.191.251:0
Tunnel1 (ldp): Targeted -> 10.131.159.251
Targeted Hellos:
10.131.191.252 -> 10.131.159.252 (ldp): active/passive, xmit/recv
LDP Id: 10.131.159.252:0
10.131.191.252 -> 10.131.159.251 (ldp): active, xmit
Enter the show mpls forwarding-table command at the PE1 router. The display shows that the outgoing
packets are untagged as a result of the LDP configuration changes.
PE1# show mpls forwarding-table 10.131.159.252
Local
tag
Outgoing
tag or VC
Prefix
or Tunnel Id
Bytes tag
switched
Outgoing
interface
Next Hop
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47
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
22
[T]
Untagged[T] 10.131.159.252/32 0
Tu1
point2point
Forwarding through a TSP tunnel.
View additional tagging info with the 'detail' option
A ping mpls command entered at the PE1 router displays the following:
PE1# ping mpls ipv4 10.131.159.252/32 repeat 1
Sending 1, 100-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
R
Success rate is 0 percent (0/1)
The ping mpls command fails. The R indicates that the sender of the MPLS echo reply had a routing
entry but no MPLS FEC. Entering the verbose keyword with the ping mpls command displays the
MPLS LSP echo reply sender address and the return code. You should be able to determine where the
breakage occurred by telnetting to the replying router and inspecting its forwarding and label tables. You
might need to look at the neighboring upstream router as well, because the breakage might be on the
upstream router.
PE1# ping mpls ipv4 10.131.159.252/32 repeat 1 verbose
Sending 1, 100-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
R
10.131.159.225, return code 6
Success rate is 0 percent (0/1)
Alternatively, use the LSP traceroute command to figure out which router caused the breakage. In the
following example, for subsequent values of TTL greater than 2, the same router keeps responding
(10.131.159.225). This suggests that the MPLS echo request keeps getting processed by the router
regardless of the TTL. Inspection of the label stack shows that P1 pops the last label and forwards the
packet to P2 as an IP packet. This explains why the packet keeps getting processed by P2. MPLS echo
request packets cannot be forwarded by use of the destination address in the IP header because the
address is set to a 127/8 address.
PE1# trace mpls ipv4 10.131.159.252/32 ttl 5
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
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48
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.230 MRU 1496 [Labels: 22/19 Exp: 0/0]
R 1 10.131.159.226 MRU 1500 [Labels: 19 Exp: 0] 40 ms
R 2 10.131.159.229 MRU 1504 [implicit-null] 28 ms
! 3 10.131.159.230 40 ms
pe1#
MTU Discovery in an LSP: Example
The following example shows the results of a trace mpls command when the LSP is formed with labels
created by LDP:
PE1# trace mpls ipv4 10.131.159.252/32
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.230 MRU 1496 [Labels: 22/19 Exp: 0/0]
R 1 10.131.159.226 MRU 1500 [Labels: 19 Exp: 0] 40 ms
R 2 10.131.159.229 MRU 1504 [implicit-null] 28 ms
! 3 10.131.159.230 40 ms
pe1#
You can determine the MRU for the LSP at each hop through the use of the show mpls forwarding detail
command:
PE1# show mpls forwarding 10.131.159.252 detail
Local
tag
22
Outgoing
Prefix
Bytes tag Outgoing
Next Hop
tag or VC
or Tunnel Id
switched
interface
19
10.131.159.252/32 0
Tu1
point2point
MAC/Encaps=14/22, MRU=1496, Tag Stack{22 19}, via Et0/0
AABBCC009700AABBCC0098008847 0001600000013000
No output feature configured
To determine how large an echo request will fit on the LSP, first calculate the size of the IP MTU by
using the show interface interface-name command:
PE1# show interface e0/0
Ethernet0/0 is up, line protocol is up
Hardware is Lance, address is aabb.cc00.9800 (bia aabb.cc00.9800)
Internet address is 10.131.191.230/30
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255
Encapsulation ARPA, loopback not set
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
49
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Keepalive set (10 sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output 00:00:01, output hang never
Last clearing of “show interface” counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
377795 packets input, 33969220 bytes, 0 no buffer
Received 231137 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
441772 packets output, 40401350 bytes, 0 underruns
0 output errors, 0 collisions, 10 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
The IP MTU in the show interface interface-name example is 1500 bytes. Subtract the number of bytes
corresponding to the label stack from the MTU number. The output of the show mpls forwarding
command indicates that the Tag stack consists of one label (21). Therefore, the largest MPLS echo
request packet that can be sent in the LSP is 1500 – (2 x 4) = 1492.
You can validate this by using the following mpls ping command:
PE1# ping mpls ipv4 10.131.159.252/32 sweep 1492 1500 1 repeat 1
Sending 1, [1492..1500]-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!QQQQQQQQ
Success rate is 11 percent (1/9), round-trip min/avg/max = 40/40/40 ms
In this command, echo packets that have a range in size from 1492 to 1500 bytes are sent to the
destination address. Only packets of 1492 bytes are sent successfully, as indicated by the exclamation
point (!). Packets of byte sizes 1493 to 1500 are source-quenched, as indicated by the Qs.
You can pad an MPLS echo request so that a payload of a given size can be tested. The pad TLV is useful
when you use the MPLS echo request to discover the MTU that is supportable by an LSP. MTU discovery
is extremely important for applications like AToM that contain non-IP payloads that cannot be
fragmented.
Tracking Packets Tagged as Implicit Null: Example
In the following example, Tunnel 1 is shut down, and only an LSP formed with LDP labels is established.
An implicit null is advertised between the P2 and PE2 routers. Entering an MPLS LSP traceroute
command at the PE1 router results in the following output that shows that packets are forwarded from
P2 to PE2 with an implicit-null label. Address 10.131.159.229 is configured for the P2 Ethernet 0/0 out
interface for the PE2 router.
PE1# trace mpls ipv4 10.131.159.252/32
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
50
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.230 MRU 1496 [Labels: 22/19 Exp: 0/0]
R 1 10.131.159.226 MRU 1500 [Labels: 19 Exp: 0] 40 ms
R 2 10.131.159.229 MRU 1504 [implicit-null] 28 ms
! 3 10.131.159.230 40 ms
pe1#
Tracking Untagged Packets: Example
Untagged cases are valid configurations for IGP LSPs that could cause problems for MPLS VPNs.
A show mpls forwarding-table command and a show mpls ldp discovery command issued at the P2
router show that LDP is properly configured:
P2# show mpls forwarding-table 10.131.159.252
Local
tag
19
Outgoing
tag or VC
Pop tag
Prefix
Bytes tag
or Tunnel Id
switched
10.131.159.252/32 0
Outgoing
interface
Et0/0
Next Hop
10.131.159.230
P2# show mpls ldp discovery
Local LDP Identifier:
10.131.159.251:0
Discovery Sources:
Interfaces:
Ethernet0/0 (ldp): xmit/recv
LDP Id: 10.131.159.252:0
Ethernet1/0 (ldp): xmit/recv
LDP Id: 10.131.191.251:0
The show mpls ldp discovery command output shows that Ethernet interface 0/0, which connects PE2
to P2, is sending and receiving packets.
If a no mpls ip command is entered on Ethernet interface 0/0, this could prevent an LDP session between
the P2 and PE2 routers from being established. A show mpls ldp discovery command entered on the PE
router shows that the MPLS LDP session with the PE2 router is down.
P2# show mpls ldp discovery
Local LDP Identifier:
10.131.159.251:0
Discovery Sources:
Interfaces:
Ethernet0/0 (ldp): xmit
Ethernet1/0 (ldp): xmit/recv
LDP Id: 10.131.191.251:0
If the MPLS LDP session to PE2 goes down, the LSP to 10.131.159.252 becomes untagged, as shown
by the show mpls forwarding-table command:
P2# show mpls forwarding-table 10.131.159.252/32
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51
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Local
tag
19
Outgoing
tag or VC
Untagged
Prefix
Bytes tag
or Tunnel Id
switched
10.131.159.252/32 864
Outgoing
interface
Et0/0
Next Hop
10.131.159.230
Untagged cases would provide an MPLS LSP traceroute reply with packets tagged with No Label, as
shown in the following display. You may need to reestablish an MPLS LSP session from interface P2 to
PE2 by entering an mpls ip command on the output interface from P2 to PE2, which is Ethernet 0/0 in
this example:
PE1# trace mpls ipv4 10.131.159.252/32
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.230 MRU 1500 [Labels: 20 Exp: 0]
R 1 10.131.159.226 MRU 1500 [Labels: 19 Exp: 0] 80 ms
R 2 10.131.159.229 MRU 1504 [No Label] 28 ms
<----No MPLS session from P2 to PE2.
! 3 10.131.159.230 40 ms
Determining Why a Packet Could Not Be Sent: Example
The following example shows a ping mpls command when an MPLS echo request is not sent. The
transmission failure is shown by the returned Qs.
PE1# ping mpls ipv4 10.0.0.1/32
Sending 5, 100-byte MPLS Echos to 10.0.0.1/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
QQQQQ
Success rate is 0 percent (0/5)
The following show mpls forwarding-table command and show ip route command demonstrate that
the IPv4 address (10.0.0.1)address is not in the LFIB or RIB routing table. Therefore, the MPLS echo
request is not sent.
PE1# show mpls forwarding-table 10.0.0.1
Local
tag
Outgoing
tag or VC
Prefix
or Tunnel Id
PE1# show ip route 10.0.0.1
% Subnet not in table
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
52
Bytes tag
switched
Outgoing
interface
Next Hop
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Detecting LSP Breaks when Load Balancing Is Enabled for IPv4 LSPs: Example
In the following examples, different paths are followed to the same destination. The output from these
examples demonstrates that load balancing occurs between the originating router and the target router.
To ensure that Ethernet interface 1/0 on the PE1 router is operational, enter the following commands on
the PE1 router:
PE1# configure terminal
Enter configuration commands, one per line.
End with CNTL/Z.
PE1(config)# interface ethernet 1/0
PE1(config-if)# no shutdown
PE1(config-if)# end
*Dec 31 19:14:10.034: %LINK-3-UPDOWN: Interface Ethernet1/0, changed state to up
*Dec 31 19:14:11.054: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet1/0,
changed state to upend
PE1#
*Dec 31 19:14:12.574: %SYS-5-CONFIG_I: Configured from console by console
*Dec 31 19:14:19.334: %OSPF-5-ADJCHG: Process 1, Nbr 10.131.159.252 on Ethernet1/0
from LOADING to FULL, Loading Done
PE1#
The following show mpls forwarding-table command displays the possible outgoing interfaces and
next hops for the prefix 10.131.159.251/32:
PE1# show mpls forwarding-table 10.131.159.251/32
Local
tag
21
Outgoing
tag or VC
19
20
Prefix
or Tunnel Id
10.131.159.251/32
10.131.159.251/32
Bytes tag
switched
0
0
Outgoing
interface
Et0/0
Et1/0
Next Hop
10.131.191.229
10.131.159.245
The following ping mpls command to 10.131.159.251/32 with a destination UDP address of 127.0.0.1
shows that the selected path has a path index of 0:
Router# ping mpls ipv4 10.131.159.251/32 destination 127.0.0.1/32
Sending 1, 100-byte MPLS Echos to 10.131.159.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
Success rate is 100 percent (1/1), round-trip
PE1#
*Dec 29 20:42:40.638: LSPV: Echo Request sent
pathindex 0, size 100
*Dec 29 20:42:40.638: 46 00 00 64 00 00 40 00
*Dec 29 20:42:40.638: 7F 00 00 01 94 04 00 00
*Dec 29 20:42:40.638: 00 01 00 00 01 02 00 00
*Dec 29 20:42:40.638: C3 9B 10 40 A3 6C 08 D4
*Dec 29 20:42:40.638: 00 01 00 09 00 01 00 05
min/avg/max = 40/40/40 ms
on IPV4 LSP, load_index 2,
FF
0D
1A
00
0A
11
AF
00
00
83
9D
0D
00
00
9F
03
AF
1C
00
FB
0A
00
00
00
20
83
4C
00
00
00
BF
14
00
00
03
FC
70
01
00
00
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
*Dec 29 20:42:40.638: 13 01
*Dec 29 20:42:40.638: AB CD
*Dec 29 20:42:40.678: LSPV:
dst 10.131.191.252, size 74
*Dec 29 20:42:40.678: AA BB
*Dec 29 20:42:40.678: 00 3C
*Dec 29 20:42:40.678: BF FC
*Dec 29 20:42:40.678: 03 00
*Dec 29 20:42:40.678: 08 D4
AB CD AB CD AB CD AB CD AB CD AB CD AB CD
AB CD
Echo packet received: src 10.131.159.225,
CC
32
0D
1A
C3
00
D6
AF
00
9B
98
00
0D
00
10
01
00
AF
1C
40
AA
FD
00
00
66
BB
11
28
00
F5
CC
15
D1
00
C3
00
37
85
01
C8
FC
0A
00
C3
01
83
01
9B
08
9F
00
10
00
E1
00
40
45
0A
02
A3
C0
83
02
6C
The following ping mpls command to 10.131.159.251/32 with a destination UDP address of 127.0.0.3
shows that the selected path has a path index of 1:
PE1# ping mpls ipv4 10.131.159.251/32 destination 127.0.0.3/32
Sending 1, 100-byte MPLS Echos to 10.131.159.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 40/40/40 ms
PE1#
*Dec 29 20:43:09.518: LSPV: Echo Request sent on IPV4 LSP, load_index 13,
pathindex 1, size 100
*Dec 29 20:43:09.518: 46 00 00 64 00 00 40 00 FF 11 9D 01 0A 83 BF FC
*Dec 29 20:43:09.518: 7F 00 00 03 94 04 00 00 0D AF 0D AF 00 4C 88 58
*Dec 29 20:43:09.518: 00 01 00 00 01 02 00 00 38 00 00 1D 00 00 00 01
*Dec 29 20:43:09.518: C3 9B 10 5D 84 B3 95 84 00 00 00 00 00 00 00 00
*Dec 29 20:43:09.518: 00 01 00 09 00 01 00 05 0A 83 9F FB 20 00 03 00
*Dec 29 20:43:09.518: 13 01 AB CD AB CD AB CD AB CD AB CD AB CD AB CD
*Dec 29 20:43:09.518: AB CD AB CD
*Dec 29 20:43:09.558: LSPV: Echo packet received: src 10.131.159.229,
dst 10.131.191.252, size 74
*Dec 29 20:43:09.558: AA BB CC 00 98 01 AA BB CC 00 FC 01 08 00 45 C0
*Dec 29 20:43:09.558: 00 3C 32 E9 00 00 FD 11 15 20 0A 83 9F E5 0A 83
*Dec 29 20:43:09.558: BF FC 0D AF 0D AF 00 28 D7 57 00 01 00 00 02 02
*Dec 29 20:43:09.558: 03 00 38 00 00 1D 00 00 00 01 C3 9B 10 5D 84 B3
*Dec 29 20:43:09.558: 95 84 C3 9B 10 5D 48 3D 50 78
To see the actual path chosen, enter the debug mpls lspv command with the packet and data keywords.
Note
The load balancing algorithm attempts to uniformly distribute packets across the available output paths
by hashing based on the IP header source and destination addresses. The selection of the address-start,
address-end, and address-increment arguments for the destination keyword may not provide the
expected results.
Specifying the Interface Through Which Echo Packets Leave a Router: Example
The following example tests load balancing from the upstream router:
Router# ping mpls ipv4 10.131.161.251/32 ttl 1 repeat 1 dsmap hashkey ipv4 bitmap 8
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Sending 1, 100-byte MPLS Echos to 10.131.161.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
L
Echo Reply received from 10.131.131.2
DSMAP 0, DS Router Addr 10.131.141.130, DS Intf Addr 10.131.141.130
Depth Limit 0, MRU 1500 [Labels: 54 Exp: 0]
Multipath Addresses:
127.0.0.3
127.0.0.5
127.0.0.7
127.0.0.8
DSMAP 1, DS Router Addr 10.131.141.2, DS Intf Addr 10.131.141.2
Depth Limit 0, MRU 1500 [Labels: 40 Exp: 0]
Multipath Addresses:
127.0.0.1
127.0.0.2
127.0.0.4
127.0.0.6
The following example validates that the transit router reported the proper results by determining the
Echo Reply sender address two hops away and checking the rx label advertised upstream:
Success rate is 0 percent (0/1)
Router# trace mpls ipv4 10.131.161.251/32 destination 127.0.0.6 ttl 2 verbose
Tracing MPLS Label Switched Path to 10.131.161.251/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.131.1 10.131.131.2 MRU 1500 [Labels: 37 Exp: 0]
L 1 10.131.131.2 10.131.141.2 MRU 1500 [Labels: 40 Exp: 0] 0 ms, ret code 8
L 2 10.131.141.2 10.131.150.2 MRU 1504 [Labels: implicit-null Exp: 0] 0 ms, ret code 8
Router#
Router# telnet 10.131.141.2
Trying 10.131.141.2 ... Open
User Access Verification
Password:
Router> en
The following example shows how the output interface keyword forces an LSP traceroute out
Ethernet interface 0/0:
Router# show mpls forwarding-table 10.131.159.251
Local
Label
20
Outgoing
Label or VC
19
18
Prefix
or Tunnel Id
10.131.159.251/32
10.131.159.251/32
Bytes Label
Switched
0
0
Outgoing
interface
Et1/0
Et0/0
Next Hop
10.131.159.245
10.131.191.229
Router# trace mpls ipv4 10.131.159.251/32
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
55
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Tracing MPLS Label Switched Path to 10.131.159.251/32, timeout is 2 seconds
Type escape sequence to abort.
0 10.131.159.246 MRU 1500 [Labels: 19 Exp: 0]
L 1 10.131.159.245 MRU 1504 [Labels: implicit-null Exp: 0] 4 ms
! 2 10.131.159.229 20 ms
Router# trace mpls ipv4 10.131.159.251/32 output-interface ethernet0/0
Tracing MPLS Label Switched Path to 10.131.159.251/32, timeout is 2 seconds
Type escape sequence to abort.
0 10.131.191.230 MRU 1500 [Labels: 18 Exp: 0]
L 1 10.131.191.229 MRU 1504 [Labels: implicit-null Exp: 0] 0 ms
! 2 10.131.159.225 1 ms
Pacing the Transmission of Packets: Example
The following example shows the pace of the transmission of packets:
Router# ping mpls ipv4 10.5.5.5/32 interval 100
Sending 5, 100-byte MPLS Echos to 10.5.5.5/32,
timeout is 2 seconds, send interval is 100 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/29/36 ms PE-802
Interrogating the Transit Router for Its Downstream Information: Example
The following example shows sample output when a router with two output paths is interrogated:
Router# ping mpls ipv4 10.161.251/32 ttl 4 repeat 1 dsmap hashkey ipv4 bitmap 16
Sending 1, 100-byte MPLS Echos to 10.131.161.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
L
Echo Reply received from 10.131.131.2
DSMAP 0, DS Router Addr 10.131.141.130, DS Intf Addr 10.131.141.130
Depth Limit 0, MRU 1500 [Labels: 54 Exp: 0]
Multipath Addresses:
127.0.0.3
127.0.0.6
127.0.0.9
127.0.0.10
127.0.0.12
127.0.0.13
127.0.0.14
127.0.0.15
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
56
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
127.0.0.16
DSMAP 1, DS Router Addr 10.131.141.2, DS Intf Addr 10.131.141.2
Depth Limit 0, MRU 1500 [Labels: 40 Exp: 0]
Multipath Addresses:
127.0.0.1
127.0.0.2
127.0.0.4
127.0.0.5
127.0.0.7
127.0.0.8
127.0.0.11
Success rate is 0 percent (0/1)
The multipath addresses cause a packet to transit to the router with the output label stack. The ping mpls
command is useful for determining the number of output paths, but when the router is more than one hop
away a router cannot always use those addresses to get the packet to transit through the router being
interrogated. This situation exists because the change in the IP header destination address may cause the
packet to be load-balanced differently by routers between the source router and the responding router.
Load balancing is affected by the source address in the IP header. The following example tests
load-balancing reporting from the upstream router:
Router# ping mpls ipv4 10.131.161.251/32 ttl 1 repeat 1 dsmap hashkey ipv4 bitmap 8
Sending 1, 100-byte MPLS Echos to 10.131.161.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
L
Echo Reply received from 10.131.131.2
DSMAP 0, DS Router Addr 10.131.141.130, DS Intf Addr 10.131.141.130
Depth Limit 0, MRU 1500 [Labels: 54 Exp: 0]
Multipath Addresses:
127.0.0.3
127.0.0.5
127.0.0.7
127.0.0.8
DSMAP 1, DS Router Addr 10.131.141.2, DS Intf Addr 10.131.141.2
Depth Limit 0, MRU 1500 [Labels: 40 Exp: 0]
Multipath Addresses:
127.0.0.1
127.0.0.2
127.0.0.4
127.0.0.6
To validate that the transit router reported the proper results, determine the Echo Reply sender address
that is two hops away and consistently check the rx label that is advertised upstream. The following is
sample output:
Success rate is 0 percent (0/1)
Router# trace mpls ipv4 10.131.161.251/32 destination 127.0.0.6 ttl 2 verbose
Tracing MPLS Label Switched Path to 10.131.161.251/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.131.1 10.131.131.2 MRU 1500 [Labels: 37 Exp: 0]
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Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
L 1 10.131.131.2 10.131.141.2 MRU 1500 [Labels: 40 Exp: 0] 0 ms, ret code 8
L 2 10.131.141.2 10.131.150.2 MRU 1504 [Labels: implicit-null Exp: 0] 0 ms, ret code 8
Router#
Router# telnet 10.131.141.2
Trying 10.131.141.2 ... Open
User Access Verification
Password:
Router> en
Router# show mpls forwarding-table 10.131.161.251
Local Outgoing
tag
tag or VC
40
Pop tag
Router#
Prefix
Bytes tag
or Tunnel Id
switched
10.131.161.251/32 268
Outgoing
interface
Et1/0
Next Hop
10.131.150.2
Interrogating a Router for Its DSMAP: Example
The following example interrogates the software and hardware forwarding layer for their depth limit that
needs to be returned in the DSMAP TLV.
Router# ping mpls ipv4 10.131.159.252/32 ttl 1 dsmap
Sending 1, 100-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!' 'L' 'D' 'M' 'P' 'R' -
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
L
Echo Reply received from 10.131.191.229
DSMAP 0, DS Router Addr 10.131.159.225, DS Intf Addr 10.131.159.225
Depth Limit 0, MRU 1508 [Labels: 18 Exp: 0]
Multipath Addresses:
127.0.0.1
127.0.0.2
127.0.0.3
127.0.0.4
127.0.0.5
127.0.0.6
127.0.0.7
127.0.0.8
127.0.0.9
127.0.0.10
127.0.0.11
127.0.0.12
127.0.0.13
127.0.0.14
127.0.0.15
127.0.0.16
127.0.0.17
127.0.0.18
127.0.0.19
127.0.0.20
127.0.0.21
127.0.0.22
127.0.0.23
127.0.0.24
127.0.0.25
127.0.0.26
127.0.0.27
127.0.0.28
127.0.0.29
127.0.0.30
127.0.0.31
127.0.0.32
Success rate is 0 percent (0/1)
Requesting that a Transit Router Validate the Target FEC Stack: Example
The following example causes a transit router to validate the target FEC stack by which an LSP to be
tested is identified:
Router# trace mpls ipv4 10.5.5.5/32 flags fec
Tracing MPLS Label Switched Path to 10.5.5.5/32, timeout is 2 seconds
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Configuration Examples for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.2.3.2 10.2.3.3 MRU 1500 [Labels: 19 Exp: 0] L 1 10.2.3.3 10.3.4.4 MRU 1500 [Labels:
19 Exp: 0] 40 ms, ret code 8 L 2 10.3.4.4 10.4.5.5 MRU 1504 [Labels: implicit-null Exp: 0]
32 ms, ret code 8 ! 3 10.4.5.5 40 ms, ret code 3
PE-802#ping
mpls ipv4 10.5.5.5/32,
Sending 5, 100-byte MPLS Echos to 10.5.5.5/32
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type
!
!
!
!
!
escape sequence
size 100, reply
size 100, reply
size 100, reply
size 100, reply
size 100, reply
to abort.
addr 10.4.5.5,
addr 10.4.5.5,
addr 10.4.5.5,
addr 10.4.5.5,
addr 10.4.5.5,
return
return
return
return
return
code
code
code
code
code
3
3
3
3
3
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/31/32 ms
Enabling LSP Ping to Detect LSP Breakages Caused by Untagged Interfaces: Example
The following example shows the extra label that is added to the end of the label stack when there is
explicit-null label shimming:
Router# trace mpls ipv4 10.131.159.252/32 force-explicit-null
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes:
'!' 'L' 'D' 'M' 'P' 'R' -
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.252 MRU 1492 [Labels: 16/18/explicit-null Exp: 0/0/0]
L 1 10.131.191.229 MRU 1508 [Labels: 18/explicit-null Exp: 0/0] 0 ms
L 2 10.131.159.225 MRU 1508 [Labels: explicit-null Exp: 0] 0 ms
! 3 10.131.159.234 4 ms
The following example shows the command output when there is not explicit-null label shimming:
PE1# trace mpls ipv4 10.131.159.252/32
Tracing MPLS Label Switched Path to 10.131.159.252/32, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
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Additional References
'L'
'D'
'M'
'P'
'R'
-
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.191.252 MRU 1496 [Labels: 16/18 Exp: 0/0]
L 1 10.131.191.229 MRU 1508 [Labels: 18 Exp: 0] 4 ms
L 2 10.131.159.225 MRU 1504 [Labels: implicit-null Exp: 0] 4 ms
! 3 10.131.159.234 4 ms
Verifying the AToM VCCV Capabilities Advertised to and Received from the
Peer: Example
The following example shows that router PE1 advertises both AToM VCCV Type 1 and Type 2 switching
capabilities and that the remote router PE2 advertises only a Type 2 switching capability.
Router# show mpls l2transport binding
Destination Address: 10.131.191.252, VC ID: 333
Local Label: 16
Cbit: 1,
VC Type: Ethernet,
GroupID: 0
MTU: 1500,
Interface Desc: n/a
VCCV Capabilities: Type 1, Type 2 <----- Locally advertised VCCV capabilities
Remote Label: 19
Cbit: 1,
VC Type: Ethernet,
GroupID: 0
MTU: 1500,
Interface Desc: n/a
VCCV Capabilities: Type 2
<-----Remotely advertised VCCV capabilities
Additional References
The following sections provide references related to the MPLS LSP Ping/Traceroute for LDP/TE, and
LSP Ping for VCCV feature.
Related Documents
Related Topic
Document Title
Usage examples for the IP ping and IP traceroute
commands
Cisco—Understanding the Ping and Traceroute Commands
Usage examples for the extended ping and extended
traceroute commands
Cisco—Using the Extended Ping and Traceroute Commands
Configuration and verification tasks for MPLS LDP
MPLS Label Distribution Protocol (LDP)
Configuration and verification tasks for AToM
Any Transport over MPLS (AToM)
Troubleshooting procedures for MPLS
Cisco—MPLS Troubleshooting
Switching services commands
Cisco IOS Switching Services Command Reference, Release 12.4
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Additional References
Related Topic
Document Title
Configuration and verification tasks for MPLS
applications
Part 3: Multiprotocol Label Switching, Cisco IOS Switching
Services Configuration Guide, Release 12.4
Automatic detection of which PE routers are added to
or removed from the Virtual Private LAN Service
(VPLS) domain
VPLS Autodiscovery: BGB Based
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported by this
feature, and support for existing MIBs has not been
modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use the Cisco MIB Locator, found at the
following URL:
http://www.cisco.com/go/mibs
RFCs
RFCs
Title
RFC 4379
Detecting Multi-Protocol Label Switched (MPLS) Data Plane
Failures
RFC 2113
IP Router Alert Option
draft-ietf-pwe3-vccv-01.txt
Pseudo-Wire (PW) Virtual Circuit Connection Verification (VCCV)
Technical Assistance
Description
Link
The Cisco Support website provides extensive online http://www.cisco.com/techsupport
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies. Access to most tools
on the Cisco Support website requires a Cisco.com user
ID and password. If you have a valid service contract
but do not have a user ID or password, you can register
on Cisco.com.
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Command Reference
Command Reference
This section documents only commands that are new or modified.
•
debug mpls lspv
•
echo
•
mpls oam
•
ping mpls
•
show mpls oam echo statistics
•
trace mpls
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debug mpls lspv
debug mpls lspv
To display information related to the MPLS LSP Ping/Traceroute feature, use the debug mpls lspv
command in privileged EXEC mode. To disable debugging output, use the no form of this command.
debug mpls lspv [tlv] [error] [event] [ipc] [packet [data | error]] [path-discovery] [multipath]
[all]
no debug mpls lspv
Syntax Description
tlv
(Optional) Displays Multiprotocol Label Switching (MPLS) echo packet
type, length, values (TLVs) information as it is being coded and decoded.
error
(Optional) Displays error conditions encountered during MPLS echo request
and echo reply encoding and decoding. See Table 7.
event
(Optional) Displays MPLS echo request and reply send and receive event
information.
ipc
(Optional) Interprocess communication. Displays debug information
regarding communication between the Route Processor and line cards.
packet data
(Optional) Displays detailed debug information for the MPLS echo packets
sent and received. This output is seen only on the originating router and the
router generating the reply.
packet error
(Optional) Displays packet errors for MPLS echo request and reply. No
output is expected for this command.
path-discovery
(Optional) Provides information regarding LSP traceroute path discovery
operations.
multipath
(Optional) Displays multipath information.
all
(Optional) Enables all the command keywords.
Command Default
MPLS LSP debugging is disabled.
Command Modes
Privileged EXEC
Command History
Release
Modification
12.0(27)S
This command was introduced.
12.4(6)T
The following keywords were added: ipc, path-discovery, multipath, and
all.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.28(SB) and
implemented on the Cisco 10000 series router.
12.0(32)SY
This command was integrated into Cisco IOS Release 12.0(32)SY.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.4(11)T
This command was integrated into Cisco IOS Release 12.4(11)T.
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debug mpls lspv
Usage Guidelines
Release
Modification
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
Use this command to monitor activity associated with the ping mpls and the trace mpls commands.
Table 7 lists the messages displayed by the debug mpls lspv error command and the reason for each
error message.
Table 7
Messages Displayed by the debug mpls lspv error Command
Message
Reason Why Message Is Displayed
Echo reply discarded because not An echo reply message is sent because the IP header indicates that
routable
the packet has the Router Alert set and the packet is not routable.
Examples
UDP checksum error, packet
discarded
A packet is received on the port being used by Label Switched
Path Verification (LSPV) and there is a checksum error on the
packet.
Invalid echo message type
An MPLS echo packet with an invalid echo message type (neither
a request nor a reply) is received.
Illegal Action
The state machine that drives the LSPV software detects an
invalid condition.
The following is sample output from the ping mpls command when LSPV event debugging is enabled:
Router# debug mpls lspv event
LSPV event debugging is on
Router# ping mpls ipv4 10.131.159.252/32 repeat 1
Sending 1, 100-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not transmitted,
'.' - timeout, 'U' - unreachable,
'R' - downstream router but not target
Type escape sequence to abort.
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 48/48/48 ms
Router#
*Dec 31 19:31:15.366: LSPV:
waiting for 2 seconds
*Dec 31 19:31:15.366: LSPV: sender_handle: 2000002D, Event Echo Requests Start,
[Idle->Waiting for Echo Reply]
*Dec 31 19:31:15.414: LSPV: sender_handle: 2000002D, Event Echo Reply Received,
[Waiting for Echo Reply->Waiting for Interval]
*Dec 31 19:31:15.466: LSPV: sender_handle: 2000002D, Event Echo Requests Cancel,
[Waiting for Interval->Idle]
Router# undebug all
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debug mpls lspv
All possible debugging has been turned off
The following is sample output from the ping mpls command when LSPV TLV debugging is enabled:
Router# debug mpls lspv tlv
LSPV tlv debugging is on
Router# ping mpls ipv4 10.131.159.252/32 repeat 1
Sending 1, 100-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not transmitted,
'.' - timeout, 'U' - unreachable,
'R' - downstream router but not target
Type escape sequence to abort.
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 40/40/40 ms
Router#
*Dec 31 19:32:32.566: LSPV: Echo Hdr encode: version 1, msg type 1, reply mode 2
, return_code 0, return_subcode 0, sender handle 9400002E, sequence number 1,
timestamp sent 14:32:32 EST Wed Dec 31 2003, timestamp rcvd 19:00:00 EST Thu Dec 31 1899
*Dec 31 19:32:32.566: LSPV: IPV4 FEC encode: destaddr 10.131.159.252/32
*Dec 31 19:32:32.566: LSPV: Pad TLV encode: type 1, size 18, pattern 0xABCD
*Dec 31 19:32:32.606: LSPV: Echo Hdr decode: version 1, msg type 2, reply mode 2,
return_code 3, return_subcode 0, sender handle 9400002E, sequence number 1,
timestamp sent 14:32:32 EST Wed Dec 31 2003, timestamp rcvd 14:32:32 EST Wed Dec 31 2003
Router# undebug all
All possible debugging has been turned off
The following is sample output from the trace mpls multipath command when LSPV multipath
debugging is on:
Router# debug mpls lspv multipath
multipath information debugging is on
Router# trace mpls multipath ipv4 10.5.5.5/32
Starting LSP Multipath Traceroute for 10.5.5.5/32
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
LL
*Aug 30 20:39:03.719: LSPV: configuring bitmask multipath, base 0x7F000000, bitmapsize 32,
start 0x7F000000, numbits 32
*Aug 30 20:39:03.719: LSPV: multipath info: info_length 4, bitmapsize 32, multipath_length
8, start 127.0.0.0, base 127.0.0.0, numbits 32
*Aug 30 20:39:03.719: LSPV: multipath info: info_length 4, bitmapsize 32, multipath_length
8, start 127.0.0.0, base 127.0.0.0, numbits 32
*Aug 30 20:39:03.719: LSPV: getnext bit_cursor 0, index 0, mask 0x80000000
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debug mpls lspv
*Aug 30 20:39:03.719: LSPV: next addr 127.0.0.1
*Aug 30 20:39:03.719: LSPV: multipath info: datagramsize 8
*Aug 30 20:39:03.719: 7F 00 00 00 FF FF FF FF
*Aug 30 20:39:04.007: LSPV: multipath info: !
Path 0 found,
output interface Et1/0 source 10.2.3.2 destination 127.0.0.1
Paths (found/broken/unexplored) (1/0/0)
Echo Request (sent/fail) (3/0)
Echo Reply (received/timeout) (3/0)
Total Time Elapsed 924 ms
Router#
*Aug 30 20:39:04.007: 7F 00 00 00 FF FF FF FF
*Aug 30 20:39:04.007: LSPV: ds map convert: rtr_id A030404, mtu 1500 intf_addr 10.3.4.4
hashkey 8, multipath length 8, info 2130706432
*Aug 30 20:39:04.007: LSPV: multipath info: hashkey type 8, base 0x7F000000, bitmapsize
32, info0 0xFFFFFFFF
*Aug 30 20:39:04.007: LSPV: multipath info: info_length 4, bitmapsize 32, multipath_length
8, start 127.0.0.1, base 127.0.0.1, numbits 32
*Aug 30 20:39:04.007: LSPV: getnext bit_cursor 0, index 0, mask 0x80000000
*Aug 30 20:39:04.007: LSPV: next addr 127.0.0.1
*Aug 30 20:39:04.007: LSPV: multipath info: datagramsize 8
*Aug 30 20:39:04.007: 7F 00 00 00 FF FF FF FF
*Aug 30 20:39:04.299: LSPV: multipath info: datagramsize 8
*Aug 30 20:39:04.299: 7F 00 00 00 FF FF FF FF
*Aug 30 20:39:04.299: LSPV: ds map convert: rtr_id A040505, mtu 1504 intf_addr 10.4.5.5
hashkey 8, multipath length 8, info 2130706432
*Aug 30 20:39:04.299: LSPV: multipath info: hashkey type 8, base 0x7F000000, bitmapsize
32, info0 0xFFFFFFFF
*Aug 30 20:39:04.299: LSPV: multipath info: info_length 4, bitmapsize 32, multipath_length
8, start 127.0.0.1, base 127.0.0.1, numbits 32
*Aug 30 20:39:04.299: LSPV: getnext bit_cursor 0, index 0, mask 0x80000000
*Aug 30 20:39:04.299: LSPV: next addr 127.0.0.1
*Aug 30 20:39:04.299: LSPV: multipath info: datagramsize 8
*Aug 30 20:39:04.299: 7F 00 00 00 FF FF FF FF
Router# undebug all
multipath information debugging is off
Related Commands
Command
Description
ping mpls
Checks MPLS LSP connectivity.
trace mpls
Discovers MPLS LSP routes that packets will actually take when traveling
to their destinations.
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echo
echo
To customize the default behavior of echo packets, use the echo command in MPLS OAM configuration
mode. To set the echo packet’s behavior to its default value, use the no form of this command.
echo {revision {3 | 4} | vendor-extension}
no echo {revision {3 | 4} | vendor-extension}
Syntax Description
revision
vendor-extension
Specifies the revision number of the echo packet’s default values. Valid
values are:
•
3—draft-ietf-mpls-lsp-ping-03 (Revision 2)
•
4—RFC 4379 Compliant (Default)
Sends Cisco-specific extension of type, length, values (TLVs) with echo
packets.
Command Default
Cisco-specific extension TLVs are sent with the echo packet. Revision 4 is the router’s default.
Command Modes
MPLS OAM configuration
Command History
Release
Modification
12.4(6)T
This command was introduced.
12.0(32)SY
This command was integrated into Cisco IOS Release 12.0(32)SY.
12.4(11)T
This command was integrated into Cisco IOS Release 12.4(11)T.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SRB
This command was integrated into Cisco IOS Release 12.2(33)SRB.
Usage Guidelines
Before you can enter the echo command, you must first enter the mpls oam command to enter MPLS
OAM configuration mode.
Specify the revision keyword only if one of the following conditions exists:
•
You want to change the revision number from the default of revision 4 to revision 3.
•
You previously entered the mpls oam command and changed the revision number to 3 and now you
want to change the revision back to 4.
To prevent failures reported by the replying router due to TLV version issues, you can use the echo
revision command to configure all routers in the core for the same version of the Internet Engineering
Task Force (IEFT) label switched paths (LSP) ping draft. For example, if the network is running draft
RFC 4379 implementations, but one router is capable of only Version 3 (Cisco Revision 3), configure all
routers in the network to operate in Revision 3 mode. Revision 3 mode applies only to Multiprotocol
Label Switching (MPLS) LSP ping or traceroute. Revision 3 mode does not support MPLS multipath
LSP traceroute.
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echo
The vendor-extension keyword is enabled by default in the router. If your network includes routers that
are not Cisco routers, you may want to disable Cisco extended TLVs. To disable Cisco extended TLVs,
specify the no echo vendor-extension command in MPLS OAM configuration mode. To enable Cisco
extended TLVs again, respecify the echo command with the vendor-extension keyword.
Examples
The following example uses Revision 3 of the echo packets and sends the vendor’s extension TLV with
the echo packet:
mpls oam
echo revision 3
echo vendor-extension
exit
Related Commands
Command
Description
mpls oam
Enters MPLS OAM configuration mode for customizing the default behavior
of echo packets.
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mpls oam
mpls oam
To enter MPLS OAM configuration mode for customizing the default behavior of echo packets, use the
mpls oam command in global configuration mode. To disable MPLS OAM functionality, use the no
format of this command.
mpls oam
no mpls oam
Syntax Description
This command has no arguments or keywords.
Command Default
Customizing the default behavior of echo packets is disabled.
Command Modes
Global configuration
Command History
Release
Modification
12.4(6)T
This command was introduced.
12.0(32)SY
This command was integrated into Cisco IOS Release 12.0(32)SY.
12.4(11)T
The no and default keywords were removed.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SRB
This command was integrated into Cisco IOS Release 12.2(33)SRB.
Usage Guidelines
After you enter the mpls oam command, you can enter the echo command in MPLS OAM configuration
mode to specify the revision number of the echo packet’s default values or to send the vendor’s extension
type, length, values (TLVs) with the echo packet.
Examples
The following example enters MPLS OAM configuration mode for customizing the default behavior of
echo packets:
mpls oam
Related Commands
Command
Description
echo
Customizes the default behavior of echo packets.
ping mpls
Checks MPLS LSP connectivity.
trace mpls
Discovers MPLS LSP routes that packets will actually take when
traveling to their destinations.
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69
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
ping mpls
To check Multiprotocol Label Switching (MPLS) label switched path (LSP) connectivity, use the ping
mpls command in privileged EXEC mode.
ping mpls {ipv4 destination-address/destination-mask-length [destination address-start
address-end increment] [ttl time-to-live] | pseudowire ipv4-address vc-id vc-id [destination
address-start address-end increment] | traffic-eng tunnel-interface tunnel-number
[ttl time-to-live]}
[revision {1 | 2 | 3 | 4}]
[source source-address]
[repeat count]
[timeout seconds]
[size packet-size | sweep minimum maximum size-increment]
[pad pattern]
[reply dscp dscp-value]
[reply pad-tlv]
[reply mode {ipv4 | router-alert}]
[interval ms]
[exp exp-bits]
[verbose]
[revision tlv-revision-number]
[force-explicit-null]
[output interface tx-interface [nexthop ip-address]]
[dsmap [hashkey {none | ipv4 bitmap bitmap-size}]]
[flags fec]
Syntax Description
ipv4
Specifies the destination type as a Label Distribution Protocol
(LDP) IPv4 address.
destination-address
Address prefix of the target to be tested.
/destination-mask-length
Number of bits in the network mask of the target address. The
slash is required.
destination
(Optional) Specifies a network 127 address.
address-start
(Optional) Beginning network 127 address.
address-end
(Optional) Ending network 127 address.
increment
(Optional) Number by which to increment the network 127
address.
ttl time-to-live
(Optional) Specifies a time-to-live (TTL) value.
pseudowire
Specifies the destination type as an Any Transport over MPLS
(AToM) virtual circuit (VC).
ipv4-address
IPv4 address of the AToM VC to be tested.
vc-id vc-id
Specifies the VC identifier of the AToM VC to be tested.
traffic-eng
Specifies the destination type as an MPLS traffic engineering
(TE) tunnel.
tunnel-interface
Tunnel interface to be tested.
tunnel-number
Tunnel interface number.
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
revision {1 | 2 | 3 | 4}
(Optional) Selects the type, length, values (TLVs) version of the
implementation. Use the revision 4 default unless attempting to
interoperate with devices running Cisco IOS Release 12.0(27)S1
or 12.0(27)S2. If you do not select a revision keyword, the
software uses the latest version.
See Table 8 in the “Revision Keyword Usage” section of the
“Usage Guidelines” section for information on when to select the
1, 2, 3, and 4 keywords.
source source-address
(Optional) Specifies the source address or name. The default
address is loopback0. This address is used as the destination
address in the MPLS echo response.
repeat count
(Optional) Specifies the number of times to resend the same
packet. The range is from 1 to 2147483647. The default is 1. If
you do not enter the repeat keyword, the software resends the
same packet five times.
timeout seconds
(Optional) Specifies the timeout interval in seconds for an MPLS
request packet. The range is from 0 to 3600. The default is 2
seconds.
size packet-size
(Optional) Specifies the size of the packet with the label stack
imposed. Packet size is the number of bytes in each ping. The
range is from 40 to 18024. The default is 100.
sweep
(Optional) Enables you to send a number of packets of different
sizes, ranging from a start size to an end size. This parameter is
similar to the Internet Control Message Protocol (ICMP) ping
sweep parameter.
minimum
(Optional) Minimum or start size for an MPLS echo packet. The
lower boundary of the sweep range varies depending on the LSP
type.
maximum
(Optional) Maximum or end size for an echo packet.
size-increment
(Optional) Number by which to increment the echo packet size.
pad pattern
(Optional) The pad TLV is used to fill the datagram so that the
MPLS echo request (User Datagram Protocol [UDP] packet with
a label stack) is the specified size.
reply dscp dscp-value
(Optional) Provides the capability to request a specific class of
service (CoS) in an echo reply by providing a differentiated
services code point (DSCP) value.
The echo reply is returned with the IP header type of service
(ToS) byte set to the value specified in the reply dscp command.
reply pad-tlv
(Optional) Tests the ability of the sender of an echo reply to
support the copy pad TLV to echo reply.
reply mode {ipv4 | router-alert}
(Optional) Specifies the reply mode for the echo request packet.
•
ipv4 = Reply with an IPv4 UDP packet (default).
•
router-alert = Reply with an IPv4 UDP packet with router
alert.
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ping mpls
interval ms
(Optional) Specifies the time, in milliseconds (ms), between
successive MPLS echo requests. This parameter allows you to
pace the transmission of packets so that the receiving router does
not drop packets. Default is 0.
exp exp-bits
(Optional) Specifies the MPLS experimental field value in the
MPLS header for an MPLS echo reply. Valid values are from 0
to 7. Default is 0.
verbose
(Optional) Displays the MPLS echo reply sender address of the
packet and displays return codes.
revision tlv-revision-number
(Optional) Cisco TLV revision number.
force-explicit-null
(Optional) Forces an explicit null label to be added to the MPLS
label stack even though the label was unsolicited.
output interface tx-interface
(Optional) Specifies the output interface for echo requests.
nexthop ip-address
(Optional) Causes packets to go through the specified next-hop
address.
dsmap
(Optional) Interrogates a transit router for downstream mapping
(DSMAP) information.
hashkey {none | ipv4 bitmap
bitmap-size}
(Optional) Allows you to control the hash key and multipath
settings. Valid values are:
•
none—There is no multipath (type 0).
•
ipv4 bitmap bitmap-size—Size of the IPv4 addresses
(type 8) bitmap.
Note
flags fec
(Optional) Allows Forward Equivalence Class (FEC) checking
on the transit router. A downstream map TLV containing the
correct received labels must be present in the echo request for
target FEC stack checking to be performed.
Note
Defaults
Time to live = 255 seconds
Revision = 4
Repeat count = 5
Timeout = 2 seconds
Packet size = 100 bytes
Sweep minimum = 100 bytes
Sweep maximum = 17,986 bytes
Sweep size increment = 100 bytes
Pad pattern = 0xABCD
Reply mode = ipv4 via UDP (2)
Send interval = 0 ms
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
72
If you enter the none keyword, multipath LSP traceroute
acts like enhanced LSP traceroute; that is, it uses
multipath LSP traceroute retry logic and consistency
checking.
Target FEC stack validation is always done at the egress
router. Be sure to use this keyword in conjunction with
the ttl keyword.
MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
Experimental bits in MPLS header = 0
Verbose = no
Request-dsmap = IPv4 bitmap hashkey
Command Modes
Privileged EXEC
Command History
Release
Modification
12.0(27)S
This command was introduced.
12.2(18)SXE
The reply dscp and reply pad-tlv keywords were added.
12.4(6)T
The following keywords were added: revision, force-explicit-null, output
interface, dsmap, hashkey, none, ipv4 bitmap, and flags fec.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB and
implemented on the Cisco 10000 series routers.
12.0(32)SY
This command was integrated into Cisco IOS Release 12.0(32)SY.
12.4(11)T
This command was integrated into Cisco IOS Release 12.4(11)T.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2. The
nexthop keyword was added.
Usage Guidelines
Note
It is recommended that you use the mpls oam global configuration command instead of this command.
Use the ping mpls command to validate, test, or troubleshoot IPv4 LDP LSPs, IPv4 Resource
Reservation Protocol (RSVP) TE tunnels, and AToM VCs.
UDP Destination Address Usage
The destination address is a valid 127/8 address. You have the option to specify a single x.y.z-address or
a range of numbers from 0.0.0 to x.y.z, where x, y, and z are numbers from 0 to 255 and correspond to
the 127.x.y.z destination address.
The MPLS echo request destination address in the UDP packet is not used to forward the MPLS packet
to the destination router. The label stack that is used to forward the echo request routes the MPLS packet
to the destination router. The 127/8 address guarantees that the packets are routed to the local host (the
default loopback address of the router processing the address) if the UDP packet destination address is
used for forwarding.
In addition, the destination address is used to adjust load balancing when the destination address of the
IP payload is used for load balancing.
Time-to-Live Usage
The time-to-live value indicates the maximum number of hops a packet should take to reach its
destination. The value in the TTL field in a packet is decremented by 1 each time the packet travels
through a router.
For MPLS LSP ping, the TTL is a value after which the packet is discarded and an MPLS echo reply is
sent back to the originating router.
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
For MPLS multipath LSP traceroute, the TTL is a maximum time-to-live value and is used to discover
the number of downstream hops to the destination router. MPLS LSP traceroute incrementally increases
the TTL value in its MPLS echo requests (TTL = 1, 2, 3, 4, ...) to accomplish this.
Downstream Map TLVs
The presence of a downstream map in an echo request is interpreted by the responding transit (not egress)
router to include downstream map information in the echo reply. Specify the ttl and dsmap keywords to
cause TTL expiry during LSP ping to interrogate a transit router for downstream information.
Revision Keyword Usage
The revision keyword allows you to issue a ping mpls ipv4, ping mpls pseudowire, or trace mpls
traffic-eng command based on the format of the TLV. Table 8 lists the revision option and usage
guidelines for each option.
Table 8
Revision Options and Option Usage Guidelines
Revision Option Option Usage Guidelines
11
Not supported in Cisco IOS Release 12.4(11)T or later releases.
Version 1 (draft-ietf-mpls-ping-03).
For a device running Cisco IOS Release 12.0(27)S3 or a later release, you must use
the revision 1 keyword when you send LSP ping or LSP traceroute commands to
devices running Cisco IOS Release 12.0(27)S1 or 12.0(27)S2.
2
Version 2 functionality was replaced by Version 3 functionality before an image was
released.
3
Version 3 (draft-ietf-mpls-ping-03).
4
•
For a device implementing Version 3 (Cisco IOS Release 12.0(27)S3 or a later
release), you must use the revision 1 keyword when you send the LSP ping or
LSP traceroute command to a device implementing Version 1 (that is, either
Cisco IOS Release 12.0(27)S1 or Release 12.0(27)S2).
•
A ping mpls pseudowire command does not work with devices running
Cisco IOS Release 12.0(27)S1 or Release 12.0(27)S2.
•
Version 8 (draft-ietf-mpls-ping-08)—Applicable before Cisco IOS
Release 12.4(11)T. All echo packet’s TLVs are formatted as specified in
Version 8.
•
RFC 4379 compliant—Applicable after Cisco IOS Release 12.4(11)T. All echo
packet’s TLVs are formatted as specified in RFC 4379.
This is the recommended version.
1. If you do not specify a revision keyword, the software uses the latest version.
Examples
The following example shows how to use the ping mpls command to test connectivity of an
IPv4 LDP LSP:
Router# ping mpls ipv4 10.131.191.252/32 repeat 5 exp 5 verbose
Sending 5, 100-byte MPLS Echos to 10.131.191.252, timeout is 2 seconds:
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
10.131.191.230, return code
!
10.131.191.230, return code
!
10.131.191.230, return code
!
10.131.191.230, return code
!
10.131.191.230, return code
3
3
3
3
3
Success rate is 100 percent (5/5), round-trip min/avg/max = 100/102/112 ms
The following example shows how to invoke the ping mpls command in the interactive mode to check
MPLS LSP connectivity:
Router# ping
Protocol [ip]: mpls
Target IPv4, pseudowire or traffic-eng [ipv4]: ipv4
Target IPv4 address: 10.131.159.252
Target mask: 255.255.255.255
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Send interval in msec [0]:
Extended commands? [no]: yes
Destination address or destination start address: 127.0.0.1
Destination end address: 127.0.0.1
Destination address increment: 0.0.0.1
Source address:
EXP bits in mpls header [0]:
Pad TLV pattern [ABCD]:
Time To Live [255]:
Reply mode ( 2-ipv4 via udp, 3-ipv4 via udp with router alert) [2]:
Reply ip header DSCP bits [0]:
Verbose mode? [no]: yes
Sweep range of sizes? [no]:
Sending 1, 100-byte MPLS Echos to 10.131.159.252/32,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
Destination address 127.0.0.1
!
10.131.159.245, return code 3
Destination address 127.0.0.1
!
10.131.159.245, return code 3
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
Destination address 127.0.0.1
!
10.131.159.245, return code 3
Success rate is 100 percent (3/3), round-trip min/avg/max = 40/48/52 ms
Note
The “Destination end address” and “Destination address increment” prompts display only if you enter
an address at the “Destination address or destination start address” prompt. Also, the “Sweep min size,”
“Sweep max size,” and “Sweep interval” prompts display only if you enter “yes” at the “Sweep range of
sizes? [no]” prompt.
The following example shows how to determine the destination address of an AToM VC:
Router# show mpls l2transport vc
Local intf
------------Et2/0
Local circuit
Dest address
VC ID
Status
----------------------- --------------- ---------- ---------Ethernet
10.131.191.252 333
UP
Router# show mpls l2transport vc detail
Local interface: Et2/0 up, line protocol up, Ethernet up
Destination address: 10.131.191.252, VC ID: 333, VC status: up
Preferred path: not configured
Default path: active
Tunnel label: imp-null, next hop 10.131.159.246
Output interface: Et1/0, imposed label stack {16}
Create time: 06:46:08, last status change time: 06:45:51
Signaling protocol: LDP, peer 10.131.191.252:0 up
MPLS VC labels: local 16, remote 16
Group ID: local 0, remote 0
MTU: local 1500, remote 1500
Remote interface description:
Sequencing: receive disabled, send disabled
VC statistics:
packet totals: receive 0, send 0
byte totals:
receive 0, send 0
packet drops: receive 0, send 0
This ping mpls command used with the pseudowire keyword can be used to test the connectivity of the
AToM VC 333 discovered in the preceding show command:
Router# ping mpls pseudowire 10.131.191.252 vc-id 333 repeat 200 size 1400
Sending 1, 100-byte MPLS Echos to 10.131.191.252, timeout is 2 seconds:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 92/92/92 ms
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
This ping is particularly useful because the VC might be up and the LDP session between the PE and its
downstream neighbor might also be up, but LDP might be configured somewhere in between. In such
cases, you can use an LSP ping to verify that the LSP is actually up.
A related point concerns the situation when a pseudowire has been configured to use a specific TE
tunnel. For example:
Router# show running-config interface ethernet 2/0
Building configuration...
Current configuration : 129 bytes
!
interface Ethernet2/0
no ip address
no ip directed-broadcast
no cdp enable
xconnect 10.131.191.252 333 pw-class test1
end
Router# show running-config | begin pseudowire
pseudowire-class test1
encapsulation mpls
preferred-path interface Tunnel0
!
In such cases, you can use an LSP ping to verify the connectivity of the LSP that a certain pseudowire
is taking, be it LDP based or a TE tunnel:
Router# ping mpls pseudowire 10.131.191.252 vc-id 333 repeat 200 size 1400
Sending 200, 1400-byte MPLS Echos to 10.131.191.252, timeout is 2 seconds:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (200/200), round-trip min/avg/max = 72/85/112 ms
You can also use the ping mpls command to verify the maximum packet size that can be successfully
sent. The following command uses a packet size of 1500 bytes:
Router# ping mpls pseudowire 10.131.191.252 vc-id 333 repeat 5 size 1500
Sending 5, 1500-byte MPLS Echos to 10.131.191.252, timeout is 2 seconds:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
ping mpls
Type escape sequence to abort.
QQQQQ
Success rate is 0 percent (0/5)
The Qs indicate that the packets are not sent.
The following command uses a packet size of 1476 bytes:
Router# ping mpls pseudowire 10.131.191.252 vc-id 333 repeat 5 size 1476
Sending 5, 1476-byte MPLS Echos to 10.131.191.252, timeout is 2 seconds:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 80/83/92 ms
The following example shows how to test the connectivity of an MPLS TE tunnel:
Router# ping mpls traffic-eng tunnel 3 repeat 5 verbose
Sending 5, 100-byte MPLS Echos to Tunnel3,
timeout is 2 seconds, send interval is 0 msec:
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
!
10.131.159.198, return code
!
10.131.159.198, return code
!
10.131.159.198, return code
!
10.131.159.198, return code
!
10.131.159.198, return code
3
3
3
3
3
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/37/40 ms
The MPLS LSP ping feature is useful if you want to verify TE tunnels before actually mapping traffic
onto them.
Related Commands
Command
Description
mpls oam
Customizes the default behavior of echo packets.
trace mpls
Discovers MPLS LSP routes that packets will actually take when traveling
to their destinations.
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
show mpls oam echo statistics
show mpls oam echo statistics
To display statistics about Multiprotocol Label Switching (MPLS) Operation, Administration, and
Maintenance (OAM) echo request packets, use the show mpls oam echo statistics command in
privileged EXEC mode.
show mpls oam echo statistics [summary]
Syntax Description
summary
Command Modes
Privileged EXEC
Command History
Release
Usage Guidelines
(Optional) Displays summary information about the echo request packets
(that is, the type, length, values (TLVs) version and the return codes of echo
packets are not displayed).
Modification
12.4(6)T
This command was introduced.
12.0(32)SY
This command was integrated into Cisco IOS Release 12.0(32)SY.
12.4(11)T
This command was integrated into Cisco IOS Release 12.4(11)T.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
You can use the show mpls oam echo statistics command to display the following:
•
Currently configured TLV version for MPLS OAM operations.
•
Return code distribution among the received MPLS echo reply packets.
•
Statistics of sent and received MPLS echo packets, and counts of incomplete packet dispatches and
timed out MPLS echo requests.
If you enter the summary keyword, the Echo Reply count shows all the echo reply packets, regardless
of whether they are valid responses to a sent request packet. Therefore, the number of return codes will
not match the number of echo reply packets received.
Examples
The following example displays sample detailed output when the summary keyword is not specified:
Router# show mpls oam echo statistics
Cisco TLV version: RFC 4379 Compliant
Return code distribution:
!—Success (3) - 5
B—Unlabeled output interface (9) - 0
D—DS map mismatch (5) - 0
f—Forward Error Correction (FEC) mismatch (10) - 0
F—No FEC mapping (4) - 0
I—Unknown upstream interface index (6) - 0
L—Labeled output interface (8) - 0
m—Unsupported TLVs (2) - 0
M—Malformed echo request (1) - 0
N—No label entry (11) - 0
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MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
show mpls oam echo statistics
p—Premature termination of link-state packet (LSP) (13) - 0
P—No receive interface label protocol (12) - 0
U—Reserved (7) - 0
x—No return code (0) - 0
X—Undefined return code - 0
Echo Requests: sent (5)/received (0)/timedout (0)/unsent (0)
Echo Replies: sent (0)/received (5)/unsent (0)
The following example displays sample output when the summary keyword is specified:
Router# show mpls oam echo statistics summary
Cisco TLV version: RFC 4379 Compliant
Echo Requests: sent (5)/received (0)/timedout (0)/unsent (0)
Echo Replies: sent (0)/received (5)/unsent (0)
Table 9 describes the significant fields shown in the displays.
Table 9
show mpls oam echo statistics Field Descriptions
Field
Description
Return Code Distribution
In each line of the return code distribution, the following
information is displayed:
Single-character code corresponding to the return code
in the received packet (for example ! or B).
•
Description of the return code (for example, Success).
•
Value of the return code (for example, (3)).
•
Number of packets received with the return code (for
example, 5).
sent
Number of MPLS echo request packets that the router sent.
timedout
Number of MPLS echo request packets that timed out.
received
Number of MPLS echo request packets that the router
received from the network.
unsent
Number of MPLS echo requests that were not forwarded due
to errors.
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•
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trace mpls
trace mpls
To discover Multiprotocol Label Switching (MPLS) label switched path (LSP) routes that packets
actually take when traveling to their destinations, use the trace mpls command in privileged EXEC
mode.
trace mpls
{ipv4 destination-address/destination-mask | traffic-eng Tunnel tunnel-number}
[timeout seconds]
[destination address-start [address-end | address-increment]]
[revision {1 | 2 | 3 | 4}]
[source source-address]
[exp exp-bits]
[ttl maximum-time-to-live]
[reply {dscp dscp-bits | mode reply-mode {ipv4 | no-reply | router-alert} | pad-tlv}]
[force-explicit-null]
[output interface tx-interface [nexthop ip-address]]
[flags fec]
[revision tlv-revision-number]
Syntax Description
ipv4
Specifies the destination type as a Label Distribution Protocol (LDP) IPv4
address.
destination-address
Address prefix of the target to be tested.
/destination-mask
Number of bits in the network mask of the target address. The slash is
required.
traffic-eng Tunnel
tunnel-number
Specifies the destination type as an MPLS traffic engineering (TE) tunnel.
timeout seconds
(Optional) Specifies the timeout interval in seconds. The range is from
0 to 3600. The default is 2 seconds.
destination
(Optional) Specifies a network 127 address.
address-start
(Optional) The beginning network 127 address.
address-end
(Optional) The ending network 127 address.
address-increment
(Optional) Number by which to increment the network 127 address.
revision {1 | 2 | 3 | 4}
(Optional) Selects the type, length, values (TLVs) version of the
implementation. Use the revision 4 default unless attempting to interoperate
with devices running Cisco IOS Release 12.0(27)S1 or 12.0(27)S2. If you do
not select a revision keyword, the software uses the latest version.
See Table 10 in the“Revision Keyword Usage” section of the “Usage
Guidelines” section for information on when to select the 1, 2, 3, and 4
keywords.
source source-address
(Optional) Specifies the source address or name. The default address is
loopback0. This address is used as the destination address in the MPLS echo
response.
exp exp-bits
(Optional) Specifies the MPLS experimental field value in the MPLS header
for an MPLS echo reply. Valid values are from 0 to 7. Default is 0.
ttl
maximum-time-to-live
(Optional) Specifies a maximum hop count.
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reply dscp dscp-bits
(Optional) Provides the capability to request a specific class of service (CoS)
in an echo reply by providing a differentiated services code point (DSCP)
value.
The echo reply is returned with the IP header ToS byte set to the value
specified in the reply dscp keyword.
reply mode reply-mode (Optional) Specifies the reply mode for the echo request packet.
The reply-mode is one of the following:
•
ipv4—Reply with an IPv4 User Datagram Protocol (UDP) packet
(default).
•
no-reply—Do not send an echo request packet in response.
•
router-alert—Reply with an IPv4 UDP packet with router alert.
reply pad-tlv
(Optional) Tests the ability of the sender of an echo reply to support the copy
pad TLV to echo reply.
force-explicit-null
(Optional) Forces an explicit null label to be added to the MPLS label stack
even though the label was unsolicited.
output interface
tx-interface
(Optional) Specifies the output interface for echo requests.
nexthop ip-address
(Optional) Causes packets to go through the specified next-hop address.
flags fec
(Optional) Requests that target Forwarding Equivalence Class (FEC) stack
validation be done at the egress router. A downstream map TLV containing
the correct received labels must be present in the echo request for target FEC
stack checking to be performed.
Note
revision
tlv-revision-number
Be sure to use this keyword in conjunction with the ttl keyword.
(Optional) Cisco TLV revision number.
Defaults
revision = 4
timeout = 2 seconds
reply mode = ipv4 via UDP (2)
Maximum time-to-live = 30 hops
Experimental bits in MPLS header = 0
Command Modes
Privileged EXEC
Command History
Release
Modification
12.0(27)S
This command was introduced.
12.2(18)SXE
The reply dscp and reply pad-tlv keywords were added.
12.4(6)T
The following keywords were added: force-explicit-null, output interface,
flags fec, and revision.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB and
implemented on the Cisco 10000 series routers.
12.0(32)SY
This command was integrated into Cisco IOS Release 12.0(32)SY.
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trace mpls
Usage Guidelines
Release
Modification
12.4(11)T
This command was integrated into Cisco IOS Release 12.4(11)T.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2. The
nexthop keyword was added.
12.2(33)SRB
This command was integrated into Cisco IOS Release 12.2(33)SRB.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
Use the trace mpls command to validate, test, or troubleshoot IPv4 LDP LSPs and IPv4 Resource
Reservation Protocol (RSVP) TE tunnels.
UDP Destination Address Usage
The destination address is a valid 127/8 address. You can specify a single address or a range of numbers
from 0.0.0 to x.y.z, where x, y, and z are numbers from 0 to 255 and correspond to the 127.x.y.z
destination address.
The MPLS echo request destination address in the UDP packet is not used to forward the MPLS packet
to the destination router. The label stack that is used to forward the echo request routes the MPLS packet
to the destination router. The 127/8 address guarantees that the packets are routed to the localhost (the
default loopback address of the router processing the address) if the UDP packet destination address is
used for forwarding.
In addition, the destination address is used to adjust load balancing when the destination address of the
IP payload is used for load balancing.
Time-to-Live Keyword Usage
The time-to-live value indicates the maximum number of hops a packet should take to reach its
destination. The value in the TTL field in a packet is decremented by 1 each time the packet travels
through a router.
For MPLS LSP ping, the TTL is a value after which the packet is discarded and an MPLS echo reply is
sent back to the originating router.
For MPLS Multipath LSP Traceroute, the TTL is a maximum time-to-live value and is used to discover
the number of downstream hops to the destination router. MPLS LSP Traceroute incrementally increases
the TTL value in its MPLS echo requests (TTL = 1, 2, 3, 4, ...) to accomplish this.
Revision Keyword Usage
The revision keyword allows you to issue a trace mpls ipv4 or trace mpls traffic-eng command based
on the format of the TLV. Table 10 lists the revision option and usage guidelines for each option.
Table 10
Revision Options and Option Usage Guidelines
Revision Option Option Usage Guidelines
11
Not supported in Cisco IOS Release 12.4(11)T or later releases.
Version 1 (draft-ietf-mpls-ping-03)
For a device running Cisco IOS Release 12.0(27)S3 or a later release, you must use
the revision 1 keyword when you send LSP ping or LSP traceroute commands to
devices running Cisco IOS Release 12.0(27)S1 or 12.0(27)S2.
2
Version 2 functionality was replaced by Version 3 functionality before any images
were shipped.
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Table 10
Revision Options and Option Usage Guidelines (continued)
Revision Option Option Usage Guidelines
3
Version 3 (draft-ietf-mpls-ping-03)
4
•
For a device implementing Version 3 (Cisco IOS Release 12.0(27)S3 or a later
release), you must use the revision 1 keyword when you send the LSP ping or
LSP traceroute command to a device implementing Version 1 (that is, either
Cisco IOS Release 12.0(27)S1 or Release 12.0(27)S2).
•
A ping mpls pseudowire command does not work with devices running
Cisco IOS Release 12.0(27)S1 or Release 12.0(27)S2.
•
Version 8 (draft-ietf-mpls-ping-08)—Applicable before Cisco IOS
Release 12.4(11)T. All echo packet’s TLVs are formatted as specified in
Version 8.
•
RFC 4379 compliant—Applicable after Cisco IOS Release 12.4(11)T. All echo
packet’s TLVs are formatted as specified in RFC 4379.
This is the recommended version.
1. If you do not specify the revision keyword, the software uses the latest version.
Examples
The following example shows how to trace packets through an MPLS LDP LSP:
Router# trace mpls ipv4 10.131.191.252/32
Alternatively, you can use the interactive mode:
Protocol [ip]: mpls
Target IPv4, pseudowire or traffic-eng [ipv4]: <ipv4 |pseudowire |tunnel> ipv4
Target IPv4 address: 10.131.191.252
Target mask: /32
Repeat [1]:
Packet size [100]:
Timeout in seconds [2]:
Extended commands? [no]: yes
Destination start address:
Destination end address:
Source address:
EXP bits in mpls header [0]:
TimeToLive [255]:
Reply mode (2-ipv4 via udp, 3-ipv4 via udp with router alert) [2]:
Reply ip header DSCP bits [0]:
Tracing MPLS Label Switched Path to 10.131.191.252/32, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.159.245 mtu 1500 []
! 1 10.131.191.252 100 ms
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trace mpls
The following example shows how to trace packets through an MPLS TE tunnel:
Router# trace mpls traffic-eng Tunnel 0
Tracing MPLS TE Label Switched Path on Tunnel0, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.159.230 mtu 1500 [Labels: 22 Exp: 0]
R 1 10.131.159.225 mtu 1500 [Labels: 22 Exp: 6] 72 ms
R 2 10.131.191.229 mtu 1504 [implicit-null] 72 ms
! 3 10.131.191.252 92 ms
Alternatively, you can use the interactive mode:
Router# traceroute
Protocol [ip]: mpls
Target IPv4 or tunnel [ipv4]: traffic-eng
Tunnel number [0]:
Repeat [1]:
Timeout in seconds [2]:
Extended commands? [no]:
Tracing MPLS TE Label Switched Path on Tunnel0, timeout is 2 seconds
Codes:
'!'
'L'
'D'
'M'
'P'
'R'
-
success, 'Q' - request not sent, '.' - timeout,
labeled output interface, 'B' - unlabeled output interface,
DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
no rx intf label prot, 'p' - premature termination of LSP,
transit router, 'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.131.159.230 mtu 1500 [Labels: 22 Exp: 0]
R 1 10.131.159.225 mtu 1500 [Labels: 22 Exp: 6] 72 ms
R 2 10.131.191.229 mtu 1504 [implicit-null] 72 ms
! 3 10.131.191.252 92 ms
Use the show running-config command to verify the configuration of Tunnel 0 (shown in bold):
Router# show running-config interface tunnel 0
Building configuration...
Current configuration : 210 bytes
!
interface Tunnel0
ip unnumbered Loopback0
no ip directed-broadcast
tunnel destination 10.131.191.252
<---- Tunnel destination IP address.
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng path-option 5 explicit name as1pe-long-path
end
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Router# show mpls traffic-eng tunnels tunnel 0 brief
Signalling Summary:
LSP Tunnels Process:
running
RSVP Process:
running
Forwarding:
enabled
Periodic reoptimization:
every 3600 seconds, next in 1369 seconds
Periodic FRR Promotion:
Not Running
Periodic auto-bw collection:
disabled
TUNNEL NAME
DESTINATION
UP IF
DOWN IF
STATE/PROT
PE_t0
10.131.191.252
Et0/0
up/up
Router# show ip cef 10.131.191.252
10.131.191.252/32, version 37, epoch 0, cached adjacency 10.131.159.246
0 packets, 0 bytes
tag information set, all rewrites owned
local tag: 21
via 10.131.159.246, Ethernet1/0, 0 dependencies
next hop 10.131.159.246, Ethernet1/0
valid cached adjacency
tag rewrite with Et1/0, 10.131.159.246, tags imposed {}
The tunnel destination has the same IP address as the one in the earlier trace IPv4 example, but the trace
takes a different path, even though tunnel 0 is not configured to forward traffic by means of autoroute or
static routing. The trace mpls traffic-eng command is powerful; it enables you to test the tunnels to
verify that they work before you map traffic onto them.
Related Commands
Command
Description
ping mpls
Checks MPLS LSP connectivity.
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Feature Information for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Feature Information for MPLS LSP Ping/Traceroute for LDP/TE,
and LSP Ping for VCCV
Table 11 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a
specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support.
Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images
support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 11
Table 11 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Feature Information for MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for VCCV
Feature Name
Releases
Feature Configuration Information
MPLS LSP Ping/Traceroute for
LDP/TE, and LSP Ping for VCCV
12.0(27)S
12.2(18)SXE
12.4(6)T
12.2(28)SB
12.0(32)SY
12.4(11)T
12.2(31)SB2
12.2(33)SRB
12.2(33)SXH
The MPLS LSP Ping/Traceroute for LDP/TE, and LSP Ping for
VCCV feature helps service providers monitor label switched
paths and quickly isolate MPLS forwarding problems.
In Cisco IOS Release 12.0(27)S, this feature was introduced.
The following commands were introduced: ping mpls and
trace mpls.
The feature was incorporated into Cisco IOS
Release 12.2(18)SXE. The following commands were
modified: ping mpls and trace mpls.
In Cisco IOS Release 12.4(6)T, the mpls oam command was
introduced and the trace mpls command was modified.
This feature was integrated into Cisco IOS
Release 12.2(28)SB.
The feature was incorporated into Cisco IOS
Release 12.0(32)SY. The show mpls oam echo statistics
command was added.
The feature was incorporated into Cisco IOS
Release 12.4(11)T. AToM Virtual Circuit Connection
Verification (VCCV) is supported. The following commands
were modified: mpls oam, ping mpls, and trace mpls.
The feature was incorporated into Cisco IOS
Release 12.2(31)SB2.
In Cisco IOS Release 12.2(33)SRB, support for FEC 129 was
added.
This feature was integrated into Cisco IOS
Release 12.2(33)SXH.
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Glossary
Glossary
FEC—Forwarding Equivalence Class. A set of packets that can be handled equivalently for forwarding
purposes and are thus suitable for binding to a single label. Examples include the set of packets destined
for one address prefix and the packets in any flow.
flow—A set of packets traveling between a pair of hosts, or between a pair of transport protocol ports
on a pair of hosts. For example, packets with the same source address, source port, destination address,
and destination port might be considered a flow.
A flow is also a stream of data traveling between two endpoints across a network (for example, from one
LAN station to another). Multiple flows can be transmitted on a single circuit.
fragmentation—The process of breaking a packet into smaller units when they are to be transmitted
over a network medium that cannot support the original size of the packet.
ICMP— Internet Control Message Protocol. A network layer Internet protocol that reports errors and
provides other information relevant to IP packet processing. It is documented in RFC 792.
LFIB—Label Forwarding Information Base. A data structure and way of managing forwarding in which
destinations and incoming labels are associated with outgoing interfaces and labels.
localhost—A name that represents the host router (device). The localhost uses the reserved loopback IP
address 127.0.0.1.
LSP—label switched path. A connection between two routers in which MPLS forwards the packets.
LSPV—Label Switched Path Verification. An LSP Ping subprocess. It encodes and decodes MPLS echo
requests and replies, and it interfaces with IP, MPLS, and AToM switching for sending and receiving
MPLS echo requests and replies. At the MPLS echo request originator router, LSPV maintains a
database of outstanding echo requests for which echo responses have not been received.
MPLS router alert label—An MPLS label of 1. An MPLS packet with a router alert label is redirected
by the router to the Route Processor (RP) processing level for handling. This allows these packets to
bypass any forwarding failures in hardware routing tables.
MRU—maximum receive unit. Maximum size, in bytes, of a labeled packet that can be forwarded
through an LSP.
MTU—maximum transmission unit. Maximum packet size, in bytes, that a particular interface can send
or receive.
punt—Redirect packets with a router alert from the line card or interface to Route Processor (RP) level
processing for handling.
PW—Pseudowire. A form of tunnel that carries the essential elements of an emulated circuit from one
provider edge (PE) router to another PE router over a packet-switched network.
RP—Route Processor. The processor module in a Cisco 7000 series router that contains the CPU, system
software, and most of the memory components that are used in the router. It is sometimes called a
supervisory processor.
RSVP—Resource Reservation Protocol. A protocol that supports the reservation of resources across an
IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature
(bandwidth, jitter, maximum burst, and so on) of the packet streams they want to receive. RSVP depends
on IPv6. Is is also known as Resource Reservation Setup Protocol.
TLV—type, length, values. A block of information included in a Cisco Discovery Protocol address.
TTL hiding—Time-to-live is a parameter you can set that indicates the maximum number of hops a
packet should take to reach its destination.
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Glossary
UDP—User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack.
UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery,
so error processing and retransmission must be handled by other protocols. UDP is defined in RFC 768.
Note
See Internetworking Terms and Acronyms for terms not included in this glossary.
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and
figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and
coincidental
© 2004-2007 Cisco Systems, Inc. All rights reserved.
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